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C# Loading non-thread-safe DLL multiple times using AppDomain or Process

I have a non-thread-safe DLL that contains static methods and data. I need to call its methods from different objects and possibly threads keeping everything separated. Google says I have to create different AppDomains (in this case one for each object calling the DLL) or create a new Process. Is that true? If yes which one is the best solution and How do I practically do it? If not is there any other solution?
Also, I have a Form instantiating the class that uses the DLL and I need to be able to access the methods inside the class from the Form. Will I be able to do that?
To make it clearer I post some code.
The DLL import goes like this:
namespace ASCOM.QHYCCD
{
public class libqhyccd
{
[DllImport("import/qhyccd.dll", EntryPoint = "InitQHYCCDResource",
CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
public unsafe static extern UInt32 InitQHYCCDResource();
[DllImport("import/qhyccd.dll", EntryPoint = "GetQHYCCDSingleFrame",
CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
public unsafe static extern UInt32 GetQHYCCDSingleFrame(IntPtr handle, ref UInt32 w, ref UInt32 h, ref UInt32 bpp, ref UInt32 channels, byte* rawArray);
public unsafe static UInt32 C_GetQHYCCDSingleFrame(IntPtr handle, ref UInt32 w, ref UInt32 h, ref UInt32 bpp, ref UInt32 channels, byte[] rawArray)
{
UInt32 ret;
fixed(byte* prawArray = rawArray)
ret = GetQHYCCDSingleFrame(handle, ref w, ref h, ref bpp, ref channels, prawArray);
return ret;
}
// a lot more stuff like this
}
}
And this is the class:
class QHYCamera
{
public static IntPtr handler;
private bool isConnected = false;
uint width, height, bpp, channels;
double chipw, chiph, pixelw, pixelh;
byte[] rawArray;
uint arrayLength;
public QHYCamera(){}
public void Connect(int index, string strid)
{
if (!isConnected)
{
//ASCOM.QHYCCD.libqhyccd.InitQHYCCDResource();
StringBuilder id = new StringBuilder(strid);
//ASCOM.QHYCCD.libqhyccd.GetQHYCCDId(index, id);
handler = ASCOM.QHYCCD.libqhyccd.OpenQHYCCD(id);
Console.WriteLine(handler.ToString());
ASCOM.QHYCCD.libqhyccd.SetQHYCCDStreamMode(handler, 0);
ASCOM.QHYCCD.libqhyccd.InitQHYCCD(handler);
ASCOM.QHYCCD.libqhyccd.GetQHYCCDChipInfo(handler, ref chipw, ref chiph, ref width, ref height, ref pixelw, ref pixelh, ref bpp);
ASCOM.QHYCCD.libqhyccd.SetQHYCCDBinMode(handler, 1, 1);
ASCOM.QHYCCD.libqhyccd.SetQHYCCDResolution(handler, 0, 0, width, height);
arrayLength = ASCOM.QHYCCD.libqhyccd.GetQHYCCDMemLength(handler);
rawArray = new byte[arrayLength];
isConnected = true;
}
}
public void Disconnect()
{
if (isConnected)
{
ASCOM.QHYCCD.libqhyccd.CloseQHYCCD(handler);
ASCOM.QHYCCD.libqhyccd.ReleaseQHYCCDResource();
isConnected = false;
}
}
public bool IsConnected()
{
return isConnected;
}
public Dictionary<string, int> GetAvailableCameras()
{
Dictionary<string, int> index_id = new Dictionary<string, int>();
for (int i = 0; i < ASCOM.QHYCCD.libqhyccd.ScanQHYCCD(); i++)
{
StringBuilder id = new StringBuilder(200);
ASCOM.QHYCCD.libqhyccd.GetQHYCCDId(i, id);
index_id.Add(id.ToString(), i);
}
return index_id;
}
public void SetExposure(double exposure)
{
if (ASCOM.QHYCCD.libqhyccd.SetQHYCCDParam(handler, StructModel.CONTROL_ID.CONTROL_EXPOSURE, exposure) == 1)
{
MessageBox.Show("Cannot set exposure", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
public void SetGain(double gain)
{
if (ASCOM.QHYCCD.libqhyccd.SetQHYCCDParam(handler, StructModel.CONTROL_ID.CONTROL_GAIN, gain) == 1)
{
MessageBox.Show("Cannot set exposure", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
public Task<Bitmap> GetBitmapAsync()
{
return Task.Run(() =>
{
return GetBitmap();
});
}
public Bitmap GetBitmap()
{
ASCOM.QHYCCD.libqhyccd.SetQHYCCDBitsMode(handler, bpp);
ASCOM.QHYCCD.libqhyccd.InitQHYCCD(handler);
ASCOM.QHYCCD.libqhyccd.ExpQHYCCDSingleFrame(handler);
uint ret = 1;
while(ret != 0)
{
ret = ASCOM.QHYCCD.libqhyccd.C_GetQHYCCDSingleFrame(handler, ref width, ref height, ref bpp, ref channels, rawArray);
}
if (ret == 0)
{
Color[] palette = new Color[256];
for (Int32 b = 0; b < 256; b++)
palette[b] = Color.FromArgb(b, b, b);
return BuildImage(rawArray, (int)width, (int)height, (int)width, PixelFormat.Format8bppIndexed, palette, null);
}
return default(Bitmap);
}
public static Bitmap BuildImage(Byte[] sourceData, Int32 width, Int32 height, Int32 stride, PixelFormat pixelFormat, Color[] palette, Color? defaultColor)
{
Bitmap newImage = new Bitmap(width, height, pixelFormat);
BitmapData targetData = newImage.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, newImage.PixelFormat);
Int32 newDataWidth = ((Image.GetPixelFormatSize(pixelFormat) * width) + 7) / 8;
Boolean isFlipped = stride < 0;
stride = Math.Abs(stride);
Int32 targetStride = targetData.Stride;
Int64 scan0 = targetData.Scan0.ToInt64();
for (Int32 y = 0; y < height; y++)
Marshal.Copy(sourceData, y * stride, new IntPtr(scan0 + y * targetStride), newDataWidth);
newImage.UnlockBits(targetData);
if (isFlipped)
newImage.RotateFlip(RotateFlipType.Rotate180FlipX);
if ((pixelFormat & PixelFormat.Indexed) != 0 && palette != null)
{
ColorPalette pal = newImage.Palette;
for (Int32 i = 0; i < pal.Entries.Length; i++)
{
if (i < palette.Length)
pal.Entries[i] = palette[i];
else if (defaultColor.HasValue)
pal.Entries[i] = defaultColor.Value;
else
break;
}
newImage.Palette = pal;
}
return newImage;
}
}
From the main form I just need to instantiate the class, spawn a new thread that calls some methods:
private void BackgroundPreviewHandler(QHYCamera camera)
{
while (camera.IsConnected())
{
Bitmap bitmap = camera.GetBitmap();
PictureBox1.Image = bitmap;
}
}
private QHYCamera visibleCam = new QHYCamera();
private QHYCamera halphaCam = new QHYCamera();
await Task.Factory.StartNew(() => BackgroundPreviewHandler(visibleCam));
await Task.Factory.StartNew(() => BackgroundPreviewHandler(halphaCam));

BitBlt convert to byte array and parse from c++ to c#

I'm trying to create a Screen Capture DLL in C++ and send the resulting Byte Arrays to C#.
I'm able to get the size returned to C# but the byte array is always null.
Here's the C++ code (made up of bits i found on the internet)
__declspec(dllexport) int ScreenCap(BYTE* *data, DWORD *size)
{
try
{
//BITMAP bmpScreen;
HWND DesktopHwnd = GetDesktopWindow();
RECT DesktopParams;
HDC DevC = GetDC(DesktopHwnd);
GetWindowRect(DesktopHwnd,&DesktopParams);
DWORD Width = DesktopParams.right - DesktopParams.left;
DWORD Height = DesktopParams.bottom - DesktopParams.top;
DWORD FileSize = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)+(sizeof(RGBTRIPLE)+1*(Width*Height*4));
*size = FileSize;
char *BmpFileData = (char*)GlobalAlloc(0x0040,FileSize);
PBITMAPFILEHEADER BFileHeader = (PBITMAPFILEHEADER)BmpFileData;
PBITMAPINFOHEADER BInfoHeader = (PBITMAPINFOHEADER)&BmpFileData[sizeof(BITMAPFILEHEADER)];
BFileHeader->bfType = 0x4D42; // BM
BFileHeader->bfSize = sizeof(BITMAPFILEHEADER);
BFileHeader->bfOffBits = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);
BInfoHeader->biSize = sizeof(BITMAPINFOHEADER);
BInfoHeader->biPlanes = 1;
BInfoHeader->biBitCount = 24;
BInfoHeader->biCompression = BI_RGB;
BInfoHeader->biHeight = Height;
BInfoHeader->biWidth = Width;
RGBTRIPLE *Image = (RGBTRIPLE*)&BmpFileData[sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)];
RGBTRIPLE color;
HDC CaptureDC = CreateCompatibleDC(DevC);
HBITMAP CaptureBitmap = CreateCompatibleBitmap(DevC,Width,Height);
SelectObject(CaptureDC,CaptureBitmap);
BOOL bRet = BitBlt(CaptureDC,0,0,Width,Height,DevC,0,0,SRCCOPY|CAPTUREBLT);
//GetDIBits(CaptureDC,CaptureBitmap,0,Height,Image,(LPBITMAPINFO)BInfoHeader, DIB_RGB_COLORS);
//GetObject(CaptureBitmap,sizeof(BITMAPFILEHEADER),&bmpScreen);
//BYTE* lpPixels = new BYTE[sizeof((LPBITMAPINFO)BInfoHeader)];
GetDIBits(CaptureDC, CaptureBitmap, 0, Height, *data, (LPBITMAPINFO)BInfoHeader, DIB_RGB_COLORS);
//DWORD Junk;
//DIBSECTION dib;
//GetObject(CaptureBitmap, sizeof(dib), (LPVOID)&dib);
//HANDLE FH = CreateFileA(BmpName,GENERIC_WRITE,FILE_SHARE_WRITE,0,CREATE_ALWAYS,0,0);
//WriteFile(FH,BmpFileData,FileSize,&Junk,0);
//CloseHandle(FH);
GlobalFree(BmpFileData);
return 1;
}
catch(char *p)
{
return 0;
}
}
And here's the C# code i'm using with the "ref" keyword.
[DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
static extern int ScreenCap(ref byte[] data, ref int size);
public static void CapScreen()
{
try
{
int hr = 0;
byte[] gData = null;
int gSize = 0;
hr = ScreenCap(ref gData, ref gSize);
int a = 1;
}
catch(Exception ex)
{
int a = 1;
}
I'm thinking there may be an issue with my GetDIBits but i'm not sure. I hope some of you guru's can set me on the right path. Thanks.
* EDIT *
OK Big thanks to both jdweng and filip for pointing me in the right direction. i'm now receiving the screen as an IntPtr and able to render it to my C# app. here's the code that now works (kind of i'll explain at the bottom)
__declspec(dllexport) char* ScreenCap(DWORD * size)
{
try
{
// Get screen dimensions
int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);
*size = ((((24 * nScreenWidth + 31)&(~31)) / 8)*nScreenHeight);
BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
// Create compatible DC, create a compatible bitmap and copy the screen using BitBlt()
HDC hdcScreen = GetDC(GetDesktopWindow());
HDC hdcCompatible = CreateCompatibleDC(hdcScreen);
HBITMAP hBmp = CreateCompatibleBitmap(hdcScreen, nScreenWidth, nScreenHeight);
//HGDIOBJ hOldBmp = SelectObject(hdcCompatible, hBmp);
HGDIOBJ hOldBmp = (HGDIOBJ) SelectObject(hdcCompatible, hBmp);
BOOL bOK = BitBlt(hdcCompatible,0,0,nScreenWidth, nScreenHeight, hdcScreen,0,0,SRCCOPY|CAPTUREBLT);
SelectObject(hdcCompatible, hOldBmp); // always select the previously selected object once done
// Get the BITMAPINFO structure from the bitmap
GetDIBits(hdcScreen, hBmp, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS);
// create the bitmap buffer
char* lpPixels = new char[MyBMInfo.bmiHeader.biSizeImage];
MyBMInfo.bmiHeader.biCompression = BI_RGB;
MyBMInfo.bmiHeader.biBitCount = 24;
// get the actual bitmap buffer
GetDIBits(hdcScreen, hBmp, 0, MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS);
//Clean Up
DeleteDC(hdcCompatible);
ReleaseDC(GetDesktopWindow(), hdcScreen);
DeleteDC(hdcScreen);
DeleteObject(hBmp);
//DeleteObject(hOldBmp);
return lpPixels;
}
catch(char *p)
{
return 0;
}
}
and the C#
[DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
static extern IntPtr ScreenCap(ref int size);
while(true)
{
int size = 0;
IntPtr ptr = ScreenCap(ref size);
byte[] result = new byte[size];
Marshal.Copy(ptr, result, 0, size);
Marshal.Release(ptr);
ptr = IntPtr.Zero;
MainWindow.Dispatcher.Invoke(new Action(
() =>
{
System.Windows.Media.ImageSource ThumbnailImage = System.Windows.Media.Imaging.BitmapSource.Create(1920, 1080, 96, 96, System.Windows.Media.PixelFormats.Bgr24, null, result, 1920 * 3);
MainWindow.canvasMain.Background = new System.Windows.Media.ImageBrush(ThumbnailImage);
result = null;
GC.Collect();
GC.WaitForPendingFinalizers();
}
), null);
}
Not sure if the problem i now face is due to doing it this way but i'm getting a major memory leak from the C++ dll now. If this is another issue all together, do i need to create a new thread?
** Edit **
Problem solved by creating a new function in the C++ dll to delete the returned char array. may not be elegant but it works.
i'd like to give a big thanks to Filip who's comments helped me to look in all sorts of places and see other things. Jdweng, your IntPtr was a god send. Not sure how i set this as answered by Jdweng. would love to award to you both.

Here is what worked for me if anyone is looking for the same. I'd like to send a big thanks to both Filip Kocica and jdweng who's suggestions gave me some ideas and helped very much. Thanks and appreciated very much.
C++
char* lpPixels;
__declspec(dllexport) BOOL ScreenCapClean()
{
delete[] lpPixels;
return 1;
}
__declspec(dllexport) char* ScreenCap(DWORD * size)
{
try
{
// Get screen dimensions
int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);
*size = ((((24 * nScreenWidth + 31)&(~31)) / 8)*nScreenHeight);
BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
MyBMInfo.bmiHeader.biWidth = nScreenWidth;
MyBMInfo.bmiHeader.biHeight = -nScreenHeight;
MyBMInfo.bmiHeader.biPlanes = 1;
MyBMInfo.bmiHeader.biBitCount = 24;
MyBMInfo.bmiHeader.biCompression = BI_RGB;
MyBMInfo.bmiHeader.biSizeImage = 0;
MyBMInfo.bmiHeader.biXPelsPerMeter = 0;
MyBMInfo.bmiHeader.biYPelsPerMeter = 0;
MyBMInfo.bmiHeader.biClrUsed = 0;
MyBMInfo.bmiHeader.biClrImportant = 0;
// Create compatible DC, create a compatible bitmap and copy the screen using BitBlt()
HDC hdcScreen = GetDC(0);
HDC hdcCompatible = CreateCompatibleDC(hdcScreen);
HBITMAP hBmp = CreateCompatibleBitmap(hdcScreen, nScreenWidth, nScreenHeight);
HGDIOBJ hOldBmp = (HGDIOBJ) SelectObject(hdcCompatible, hBmp);
BOOL bOK = BitBlt(hdcCompatible,0,0,nScreenWidth, nScreenHeight, hdcScreen,0,0,SRCCOPY|CAPTUREBLT);
SelectObject(hdcCompatible, hOldBmp); // always select the previously selected object once done
// Get the BITMAPINFO structure from the bitmap
GetDIBits(hdcScreen, hBmp, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS);
// create the bitmap buffer
lpPixels = new char[MyBMInfo.bmiHeader.biSizeImage];
MyBMInfo.bmiHeader.biCompression = BI_RGB;
MyBMInfo.bmiHeader.biBitCount = 24;
// get the actual bitmap buffer
GetDIBits(hdcScreen, hBmp, 0, -MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS);
//Clean Up
ReleaseDC(0, hdcScreen);
ReleaseDC(0, hdcCompatible);
DeleteDC(hdcCompatible);
DeleteDC(hdcScreen);
DeleteObject(hBmp);
DeleteObject(hOldBmp);
return lpPixels;
}
catch(char *p)
{
return 0;
}
}
C#
[DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
static extern IntPtr ScreenCap(ref int size);
[DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
static extern bool ScreenCapClean();
int size = 0;
IntPtr ptr = ScreenCap(ref size);
byte[] result = new byte[size];
Marshal.Copy(ptr, result, 0, size);
Marshal.Release(ptr);
ptr = IntPtr.Zero;
//After doing what's required with the byte array
bool hr = ScreenCapClean();

Saving Transparent PNG as Transparent GIF

I'm trying to Resizing a Transparent png and saving it as a single frame gif image.
Let skip resizing part, while you try to save a Transparent png as gif, you will see a black background in output gif:
Bitmap n = new Bitmap(targetPngPath);
n.Save(#"C:\1.gif", ImageFormat.Gif);
yes, I can make that black background into white, but it is not what I'm looking for. Even I can remove the black color using MakeTransparent Method, But it will remove about every black color in image and we will not have a standard transparent image.
we also can do a TRICK saving gif image, we keep extension in filename but we will save it as PNG Format like this:
n.Save(#"C:\1.gif", ImageFormat.Png);
But it is not also standard.
So is there any way to safely save a transparent png as a gif image with transparency?
PNG =
GIF =
GIF Saved With Photoshop =

This is because the built-in GIF encoder cannot handle the source well, unless it is already a 8 bpp image. You must convert your PNG image to a 256 color image first, then you can save it correctly with the GIF encoder.
public static void SaveGif(string fileName, Image image)
{
int bpp = Image.GetPixelFormatSize(image.PixelFormat);
if (bpp == 8)
{
image.Save(fileName, ImageFormat.Gif);
return;
}
// 1 and 4 bpp images are need to be converted, too; otherwise, gif encoder encodes the image from 32 bpp image resulting 256 color, no transparency
if (bpp < 8)
{
using (Image image8Bpp = ConvertPixelFormat(image, PixelFormat.Format8bppIndexed, null))
{
image8Bpp.Save(fileName, ImageFormat.Gif);
return;
}
}
// high/true color bitmap: obtaining the colors
// Converting always to 8 bpp pixel format; otherwise, gif encoder would convert it to 32 bpp first.
// With 8 bpp, gif encoder will preserve transparency and will save compact palette
// Note: This works well for 256 color images in a 32bpp bitmap. Otherwise, you might try to pass null as palette so a default palette will be used.
Color[] palette = GetColors((Bitmap)image, 256);
using (Image imageIndexed = ConvertPixelFormat(image, PixelFormat.Format8bppIndexed, palette))
{
imageIndexed.Save(fileName, ImageFormat.Gif);
}
}
// TODO: Use some quantizer
private static Color[] GetColors(Bitmap bitmap, int maxColors)
{
if (bitmap == null)
throw new ArgumentNullException("bitmap");
if (maxColors < 0)
throw new ArgumentOutOfRangeException("maxColors");
HashSet<int> colors = new HashSet<int>();
PixelFormat pixelFormat = bitmap.PixelFormat;
if (Image.GetPixelFormatSize(pixelFormat) <= 8)
return bitmap.Palette.Entries;
// 32 bpp source: the performant variant
if (pixelFormat == PixelFormat.Format32bppRgb ||
pixelFormat == PixelFormat.Format32bppArgb ||
pixelFormat == PixelFormat.Format32bppPArgb)
{
BitmapData data = bitmap.LockBits(new Rectangle(Point.Empty, bitmap.Size), ImageLockMode.ReadOnly, pixelFormat);
try
{
unsafe
{
byte* line = (byte*)data.Scan0;
for (int y = 0; y < data.Height; y++)
{
for (int x = 0; x < data.Width; x++)
{
int c = ((int*)line)[x];
// if alpha is 0, adding the transparent color
if ((c >> 24) == 0)
c = 0xFFFFFF;
if (colors.Contains(c))
continue;
colors.Add(c);
if (colors.Count == maxColors)
return colors.Select(Color.FromArgb).ToArray();
}
line += data.Stride;
}
}
}
finally
{
bitmap.UnlockBits(data);
}
}
else
{
// fallback: getpixel
for (int y = 0; y < bitmap.Height; y++)
{
for (int x = 0; x < bitmap.Width; x++)
{
int c = bitmap.GetPixel(x, y).ToArgb();
if (colors.Contains(c))
continue;
colors.Add(c);
if (colors.Count == maxColors)
return colors.Select(Color.FromArgb).ToArray();
}
}
}
return colors.Select(Color.FromArgb).ToArray();
}
private static Image ConvertPixelFormat(Image image, PixelFormat newPixelFormat, Color[] palette)
{
if (image == null)
throw new ArgumentNullException("image");
PixelFormat sourcePixelFormat = image.PixelFormat;
int bpp = Image.GetPixelFormatSize(newPixelFormat);
if (newPixelFormat == PixelFormat.Format16bppArgb1555 || newPixelFormat == PixelFormat.Format16bppGrayScale)
throw new NotSupportedException("This pixel format is not supported by GDI+");
Bitmap result;
// non-indexed target image (transparency preserved automatically)
if (bpp > 8)
{
result = new Bitmap(image.Width, image.Height, newPixelFormat);
using (Graphics g = Graphics.FromImage(result))
{
g.DrawImage(image, 0, 0, image.Width, image.Height);
}
return result;
}
int transparentIndex;
Bitmap bmp;
// indexed colors: using GDI+ natively
RGBQUAD[] targetPalette = new RGBQUAD[256];
int colorCount = InitPalette(targetPalette, bpp, (image is Bitmap) ? image.Palette : null, palette, out transparentIndex);
BITMAPINFO bmi = new BITMAPINFO();
bmi.icHeader.biSize = (uint)Marshal.SizeOf(typeof(BITMAPINFOHEADER));
bmi.icHeader.biWidth = image.Width;
bmi.icHeader.biHeight = image.Height;
bmi.icHeader.biPlanes = 1;
bmi.icHeader.biBitCount = (ushort)bpp;
bmi.icHeader.biCompression = BI_RGB;
bmi.icHeader.biSizeImage = (uint)(((image.Width + 7) & 0xFFFFFFF8) * image.Height / (8 / bpp));
bmi.icHeader.biXPelsPerMeter = 0;
bmi.icHeader.biYPelsPerMeter = 0;
bmi.icHeader.biClrUsed = (uint)colorCount;
bmi.icHeader.biClrImportant = (uint)colorCount;
bmi.icColors = targetPalette;
bmp = (image as Bitmap) ?? new Bitmap(image);
// Creating the indexed bitmap
IntPtr bits;
IntPtr hbmResult = CreateDIBSection(IntPtr.Zero, ref bmi, DIB_RGB_COLORS, out bits, IntPtr.Zero, 0);
// Obtaining screen DC
IntPtr dcScreen = GetDC(IntPtr.Zero);
// DC for the original hbitmap
IntPtr hbmSource = bmp.GetHbitmap();
IntPtr dcSource = CreateCompatibleDC(dcScreen);
SelectObject(dcSource, hbmSource);
// DC for the indexed hbitmap
IntPtr dcTarget = CreateCompatibleDC(dcScreen);
SelectObject(dcTarget, hbmResult);
// Copy content
BitBlt(dcTarget, 0, 0, image.Width, image.Height, dcSource, 0, 0, 0x00CC0020 /*TernaryRasterOperations.SRCCOPY*/);
// obtaining result
result = Image.FromHbitmap(hbmResult);
result.SetResolution(image.HorizontalResolution, image.VerticalResolution);
// cleanup
DeleteDC(dcSource);
DeleteDC(dcTarget);
ReleaseDC(IntPtr.Zero, dcScreen);
DeleteObject(hbmSource);
DeleteObject(hbmResult);
ColorPalette resultPalette = result.Palette;
bool resetPalette = false;
// restoring transparency
if (transparentIndex >= 0)
{
// updating palette if transparent color is not actually transparent
if (resultPalette.Entries[transparentIndex].A != 0)
{
resultPalette.Entries[transparentIndex] = Color.Transparent;
resetPalette = true;
}
ToIndexedTransparentByArgb(result, bmp, transparentIndex);
}
if (resetPalette)
result.Palette = resultPalette;
if (!ReferenceEquals(bmp, image))
bmp.Dispose();
return result;
}
private static int InitPalette(RGBQUAD[] targetPalette, int bpp, ColorPalette originalPalette, Color[] desiredPalette, out int transparentIndex)
{
int maxColors = 1 << bpp;
// using desired palette
Color[] sourcePalette = desiredPalette;
// or, using original palette if it has fewer or the same amount of colors as requested
if (sourcePalette == null && originalPalette != null && originalPalette.Entries.Length > 0 && originalPalette.Entries.Length <= maxColors)
sourcePalette = originalPalette.Entries;
// or, using default system palette
if (sourcePalette == null)
{
using (Bitmap bmpReference = new Bitmap(1, 1, GetPixelFormat(bpp)))
{
sourcePalette = bmpReference.Palette.Entries;
}
}
// it is ignored if source has too few colors (rest of the entries will be black)
transparentIndex = -1;
bool hasBlack = false;
int colorCount = Math.Min(maxColors, sourcePalette.Length);
for (int i = 0; i < colorCount; i++)
{
targetPalette[i] = new RGBQUAD(sourcePalette[i]);
if (transparentIndex == -1 && sourcePalette[i].A == 0)
transparentIndex = i;
if (!hasBlack && (sourcePalette[i].ToArgb() & 0xFFFFFF) == 0)
hasBlack = true;
}
// if transparent index is 0, relocating it and setting transparent index to 1
if (transparentIndex == 0)
{
targetPalette[0] = targetPalette[1];
transparentIndex = 1;
}
// otherwise, setting the color of transparent index the same as the previous color, so it will not be used during the conversion
else if (transparentIndex != -1)
{
targetPalette[transparentIndex] = targetPalette[transparentIndex - 1];
}
// if black color is not found in palette, counting 1 extra colors because it can be used in conversion
if (colorCount < maxColors && !hasBlack)
colorCount++;
return colorCount;
}
private unsafe static void ToIndexedTransparentByArgb(Bitmap target, Bitmap source, int transparentIndex)
{
int sourceBpp = Image.GetPixelFormatSize(source.PixelFormat);
int targetBpp = Image.GetPixelFormatSize(target.PixelFormat);
BitmapData dataTarget = target.LockBits(new Rectangle(Point.Empty, target.Size), ImageLockMode.ReadWrite, target.PixelFormat);
BitmapData dataSource = source.LockBits(new Rectangle(Point.Empty, source.Size), ImageLockMode.ReadOnly, source.PixelFormat);
try
{
byte* lineSource = (byte*)dataSource.Scan0;
byte* lineTarget = (byte*)dataTarget.Scan0;
bool is32Bpp = sourceBpp == 32;
// scanning through the lines
for (int y = 0; y < dataSource.Height; y++)
{
// scanning through the pixels within the line
for (int x = 0; x < dataSource.Width; x++)
{
// testing if pixel is transparent (applies both argb and pargb)
if (is32Bpp && ((uint*)lineSource)[x] >> 24 == 0
|| !is32Bpp && ((ulong*)lineSource)[x] >> 48 == 0UL)
{
switch (targetBpp)
{
case 8:
lineTarget[x] = (byte)transparentIndex;
break;
case 4:
// First pixel is the high nibble
int pos = x >> 1;
byte nibbles = lineTarget[pos];
if ((x & 1) == 0)
{
nibbles &= 0x0F;
nibbles |= (byte)(transparentIndex << 4);
}
else
{
nibbles &= 0xF0;
nibbles |= (byte)transparentIndex;
}
lineTarget[pos] = nibbles;
break;
case 1:
// First pixel is MSB.
pos = x >> 3;
byte mask = (byte)(128 >> (x & 7));
if (transparentIndex == 0)
lineTarget[pos] &= (byte)~mask;
else
lineTarget[pos] |= mask;
break;
}
}
}
lineSource += dataSource.Stride;
lineTarget += dataTarget.Stride;
}
}
finally
{
target.UnlockBits(dataTarget);
source.UnlockBits(dataSource);
}
}
private static PixelFormat GetPixelFormat(int bpp)
{
switch (bpp)
{
case 1:
return PixelFormat.Format1bppIndexed;
case 4:
return PixelFormat.Format4bppIndexed;
case 8:
return PixelFormat.Format8bppIndexed;
case 16:
return PixelFormat.Format16bppRgb565;
case 24:
return PixelFormat.Format24bppRgb;
case 32:
return PixelFormat.Format32bppArgb;
case 48:
return PixelFormat.Format48bppRgb;
case 64:
return PixelFormat.Format64bppArgb;
default:
throw new ArgumentOutOfRangeException("bpp");
}
}
And the native types and methods:
private const int BI_RGB = 0;
private const int DIB_RGB_COLORS = 0;
[DllImport("gdi32.dll", CharSet = CharSet.Auto)]
private static extern IntPtr CreateDIBSection(IntPtr hdc, [In] ref BITMAPINFO pbmi, int iUsage, out IntPtr ppvBits, IntPtr hSection, uint dwOffset);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern IntPtr GetDC(IntPtr hWnd);
[DllImport("gdi32.dll", SetLastError = true)]
private static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);
[DllImport("gdi32.dll", SetLastError = true)]
private static extern IntPtr CreateCompatibleDC(IntPtr hdc);
[DllImport("gdi32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, uint dwRop);
[DllImport("gdi32.dll")]
private static extern bool DeleteDC(IntPtr hdc);
[DllImport("gdi32.dll", SetLastError = true)]
private static extern bool DeleteObject(IntPtr hObject);
[DllImport("user32.dll")]
private static extern bool ReleaseDC(IntPtr hWnd, IntPtr hDC);
[StructLayout(LayoutKind.Sequential)]
private struct RGBQUAD
{
internal byte rgbBlue;
internal byte rgbGreen;
internal byte rgbRed;
internal byte rgbReserved;
internal RGBQUAD(Color color)
{
rgbRed = color.R;
rgbGreen = color.G;
rgbBlue = color.B;
rgbReserved = 0;
}
}
[StructLayout(LayoutKind.Sequential)]
private struct BITMAPINFO
{
public BITMAPINFOHEADER icHeader;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)]
public RGBQUAD[] icColors;
}
[StructLayout(LayoutKind.Sequential)]
private struct BITMAPINFOHEADER
{
internal uint biSize;
internal int biWidth;
internal int biHeight;
internal ushort biPlanes;
internal ushort biBitCount;
internal uint biCompression;
internal uint biSizeImage;
internal int biXPelsPerMeter;
internal int biYPelsPerMeter;
internal uint biClrUsed;
internal uint biClrImportant;
}
Update:
My Drawing Libraries are now free to download. It makes a SaveAsGif extension method available on the Image type:
using KGySoft.Drawing;
/// ...
using (var stream = new FileStream(targetPngPath, FileMode.Create))
{
// You can either use an arbitrary palette,
myPngBitmap.SaveAsGif(stream, myPngBitmap.GetColors(256));
// or, you can let the built-in encoder use dithering with a fixed palette.
// Pixel format is adjusted so transparency will be preserved.
myPngBitmap.SaveAsGif(stream, allowDithering: true);
}

This may help.
The Bitmap class does not save correctly with transparency.
You need to cast Bitmap to Image.
c# Bitmap.Save transparancy doesn't save in png
There are comments on the internet about .NET not saving Bitmaps with Transparency correctly .
Here is a good link for further reading, too much code to post.
http://forums.asp.net/t/1057792.aspx?ASP+NET+C+Making+an+Image+transparent

Get image as Image Class with twain in c#

I can connect and get images from my device with twaindotnet. But I want to handle the images as Image class. When I try something like this:
...
ArrayList pics = tw.TransferPictures();
EndingScan();
tw.CloseSrc();
if(pics.Count > 0) {
IntPtr img = (IntPtr) pics[ 0 ];
PicForm newpic = new PicForm( img );
Image r = Image.FromHbitmap(img, this.Handle);
picturebox.Image = r;
}
...
I'm getting an error as "Error:Generic Error Occured in GDI+" on the line ,
Image r = Image.FromHbitmap(img, this.Handle);
So where am I wrong? How can I get as an Image the image?

I too found out that calling Image.FromHbitmap is not enough.
I had a look in the TwainDotNet library you mentioned and there I found the BitmapRenderer class.
Pulling out just the relevant bit it is easy enough to use that to create a simple static method that you can pass in the IntPtr you get from TWAIN (in your case your img variable) and convert it to a Bitmap. You, therefore, call it like so:
Image r = TwainBitmapConvertor.ToBitmap(img);
and here is the code (it only works on x86 and needs tidying but it does the job):
public static class TwainBitmapConvertor
{
[StructLayout(LayoutKind.Sequential, Pack = 2)]
private class BitmapInfoHeader
{
public int Size;
public int Width;
public int Height;
public short Planes;
public short BitCount;
public int Compression;
public int SizeImage;
public int XPelsPerMeter;
public int YPelsPerMeter;
public int ClrUsed;
public int ClrImportant;
}
[DllImport("gdi32.dll", ExactSpelling = true)]
private static extern int SetDIBitsToDevice(IntPtr hdc,
int xdst, int ydst, int width, int height, int xsrc,
int ysrc, int start, int lines, IntPtr bitsptr,
IntPtr bmiptr, int color);
[DllImport("kernel32.dll", ExactSpelling = true)]
private static extern IntPtr GlobalLock(IntPtr handle);
[DllImport("kernel32.dll", ExactSpelling = true)]
private static extern bool GlobalUnlock(IntPtr handle);
[DllImport("kernel32.dll", ExactSpelling = true)]
private static extern IntPtr GlobalFree(IntPtr handle);
public static Bitmap ToBitmap(IntPtr dibHandle)
{
var bitmapPointer = GlobalLock(dibHandle);
var bitmapInfo = new BitmapInfoHeader();
Marshal.PtrToStructure(bitmapPointer, bitmapInfo);
var rectangle = new Rectangle();
rectangle.X = rectangle.Y = 0;
rectangle.Width = bitmapInfo.Width;
rectangle.Height = bitmapInfo.Height;
if (bitmapInfo.SizeImage == 0)
{
bitmapInfo.SizeImage =
((((bitmapInfo.Width * bitmapInfo.BitCount) + 31) & ~31) >> 3)
* bitmapInfo.Height;
}
// The following code only works on x86
Debug.Assert(Marshal.SizeOf(typeof(IntPtr)) == 4);
int pixelInfoPointer = bitmapInfo.ClrUsed;
if ((pixelInfoPointer == 0) && (bitmapInfo.BitCount <= 8))
{
pixelInfoPointer = 1 << bitmapInfo.BitCount;
}
pixelInfoPointer = (pixelInfoPointer * 4) + bitmapInfo.Size
+ bitmapPointer.ToInt32();
IntPtr pixelInfoIntPointer = new IntPtr(pixelInfoPointer);
Bitmap bitmap = new Bitmap(rectangle.Width, rectangle.Height);
using (Graphics graphics = Graphics.FromImage(bitmap))
{
IntPtr hdc = graphics.GetHdc();
try
{
SetDIBitsToDevice(hdc,
0, 0, rectangle.Width, rectangle.Height, 0, 0, 0,
rectangle.Height, pixelInfoIntPointer, bitmapPointer, 0);
}
finally
{
graphics.ReleaseHdc(hdc);
}
}
bitmap.SetResolution(PpmToDpi(bitmapInfo.XPelsPerMeter),
PpmToDpi(bitmapInfo.YPelsPerMeter));
GlobalUnlock(dibHandle);
GlobalFree(dibHandle);
return bitmap;
}
private static float PpmToDpi(double pixelsPerMeter)
{
double pixelsPerMillimeter = (double)pixelsPerMeter / 1000.0;
double dotsPerInch = pixelsPerMillimeter * 25.4;
return (float)Math.Round(dotsPerInch, 2);
}
}

Assuming that tw.TransferPictures() returns an array of bitmap handles, then change Image r = ... to:
Image r = Image.FromHbitmap(img);
The second argument to FromHbitmap is a handle to a GDI palette, which I doubt you have.

How to read the Color of a Screen Pixel

Okay, I am looking for a function or something that will read the color of a certain pixel on my monitor, and when that color is detected, another function will be enabled. I figure using RGB. All help appreciated. Thank You.

This is the most efficient: It grabs a pixel at the location of the cursor, and doesn't rely on only having one monitor.
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.Diagnostics;
namespace FormTest
{
public partial class Form1 : Form
{
[DllImport("user32.dll")]
static extern bool GetCursorPos(ref Point lpPoint);
[DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
public static extern int BitBlt(IntPtr hDC, int x, int y, int nWidth, int nHeight, IntPtr hSrcDC, int xSrc, int ySrc, int dwRop);
public Form1()
{
InitializeComponent();
}
private void MouseMoveTimer_Tick(object sender, EventArgs e)
{
Point cursor = new Point();
GetCursorPos(ref cursor);
var c = GetColorAt(cursor);
this.BackColor = c;
if (c.R == c.G && c.G < 64 && c.B > 128)
{
MessageBox.Show("Blue");
}
}
Bitmap screenPixel = new Bitmap(1, 1, PixelFormat.Format32bppArgb);
public Color GetColorAt(Point location)
{
using (Graphics gdest = Graphics.FromImage(screenPixel))
{
using (Graphics gsrc = Graphics.FromHwnd(IntPtr.Zero))
{
IntPtr hSrcDC = gsrc.GetHdc();
IntPtr hDC = gdest.GetHdc();
int retval = BitBlt(hDC, 0, 0, 1, 1, hSrcDC, location.X, location.Y, (int)CopyPixelOperation.SourceCopy);
gdest.ReleaseHdc();
gsrc.ReleaseHdc();
}
}
return screenPixel.GetPixel(0, 0);
}
}
}
Now, obviously, you don't have to use the cursor's current location, but this is the general idea.
EDIT:
Given the above GetColorAt function you can poll a certain pixel on the screen in a safe, performance friendly way like this:
private void PollPixel(Point location, Color color)
{
while(true)
{
var c = GetColorAt(location);
if (c.R == color.R && c.G == color.G && c.B == color.B)
{
DoAction();
return;
}
// By calling Thread.Sleep() without a parameter, we are signaling to the
// operating system that we only want to sleep long enough for other
// applications. As soon as the other apps yield their CPU time, we will
// regain control.
Thread.Sleep()
}
}
You can wrap that in a Thread if you want, or execute it from a Console application. "Whatever suits your fancy," I guess.

Most answers here use the very same source of that pixel (desktop dc).
The key function is GetPixel.
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr GetDesktopWindow();
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr GetWindowDC(IntPtr window);
[DllImport("gdi32.dll", SetLastError = true)]
public static extern uint GetPixel(IntPtr dc, int x, int y);
[DllImport("user32.dll", SetLastError = true)]
public static extern int ReleaseDC(IntPtr window, IntPtr dc);
public static Color GetColorAt(int x, int y)
{
IntPtr desk = GetDesktopWindow();
IntPtr dc = GetWindowDC(desk);
int a = (int) GetPixel(dc, x, y);
ReleaseDC(desk, dc);
return Color.FromArgb(255, (a >> 0) & 0xff, (a >> 8) & 0xff, (a >> 16) & 0xff);
}
I think this is the cleanest and quickest way.
Note:
If you have modified the default text size among the Display Settings on Windows to increase readability on a high resolution display, the coordinate parameters of GetPixel() need to be adjusted the same way. For example, if the cursor location is (x,y) with 150% of text size on Windows 7, you need to call GetPixel(x*1.5, y*1.5) to get the color of the pixel under the cursor.

This function is shorter and can achieve the same result using System.Drawing, without Pinvoke.
Color GetColorAt(int x, int y)
{
Bitmap bmp = new Bitmap(1, 1);
Rectangle bounds = new Rectangle(x, y, 1, 1);
using (Graphics g = Graphics.FromImage(bmp))
g.CopyFromScreen(bounds.Location, Point.Empty, bounds.Size);
return bmp.GetPixel(0, 0);
}

Please check this two different functions I have used in one of my previous projects :
1) This function takes snapshot of Desktop
private void CaptureScreenAndSave(string strSavePath)
{
//SetTitle("Capturing Screen...");
Bitmap bmpScreenshot;
Graphics gfxScreenshot;
bmpScreenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height,System.Drawing.Imaging.PixelFormat.Format32bppArgb);
gfxScreenshot = Graphics.FromImage(bmpScreenshot);
gfxScreenshot.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0, 0, Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);
MemoryStream msIn = new MemoryStream();
bmpScreenshot.Save(msIn, System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[0], null);
msIn.Close();
byte[] buf = msIn.ToArray();
MemoryStream msOut = new MemoryStream();
msOut.Write(buf, 0, buf.Length);
msOut.Position = 0;
Bitmap bmpOut = new Bitmap(msOut);
try
{
bmpOut.Save(strSavePath, System.Drawing.Imaging.ImageFormat.Bmp);
//SetTitle("Capturing Screen Image Saved...");
}
catch (Exception exp)
{
}
finally
{
msOut.Close();
}
}
2) This function takes an image in input and calculates RGB average of pixel range given.
double GetRGBAverageForPixelRange( int istartRange, int iEndRange, Bitmap oBitmap )
{
double dRetnVal = 0 ;
Color oTempColor ;
int i, j ;
for( int iCounter = istartRange ; iCounter < iEndRange ; iCounter++ )
{
i = (iCounter % (oBitmap.Width));
j = ( iCounter / ( oBitmap.Width ) ) ;
if (i >= 0 && j >= 0 && i < oBitmap.Width && j < oBitmap.Height )
{
oTempColor = oBitmap.GetPixel(i, j);
dRetnVal = dRetnVal + oTempColor.ToArgb();
}
}
return dRetnVal ;
}
This two functions together might solve your problem. Happy Coding :)
EDIT : Please note that GetPixel is very slow function. I will think twice befor using it.

As far as I know the easiest way to do this is to:
take a screenshot
look at the bitmap and get the pixel color
Edit
There is probably no way to "wait" until the pixel changes to a certain color. Your program will probably have to just loop and check it every so often until it sees the color.
For example:
while(!IsPixelColor(x, y, color))
{
//probably best to add a sleep here so your program doesn't use too much CPU
}
DoAction();
EDIT 2
Here is some sample code you can modify. This code just changes the color of a label based on the current color in a given pixel. This code avoids the handle leak mentioned.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Runtime.InteropServices;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
[DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
public static extern int BitBlt(IntPtr hDC, int x, int y, int nWidth, int nHeight, IntPtr hSrcDC, int xSrc, int ySrc, int dwRop);
Thread t;
int x, y;
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
x = 20;
y = 50;
t = new Thread(update);
t.Start();
}
private void update()
{
Bitmap screenCopy = new Bitmap(1, 1);
using (Graphics gdest = Graphics.FromImage(screenCopy))
{
while (true)
{
//g.CopyFromScreen(new Point(0, 0), new Point(0, 0), new Size(256, 256));
using (Graphics gsrc = Graphics.FromHwnd(IntPtr.Zero))
{
IntPtr hSrcDC = gsrc.GetHdc();
IntPtr hDC = gdest.GetHdc();
int retval = BitBlt(hDC, 0, 0, 1, 1, hSrcDC, x, y, (int)CopyPixelOperation.SourceCopy);
gdest.ReleaseHdc();
gsrc.ReleaseHdc();
}
Color c = Color.FromArgb(screenCopy.GetPixel(0, 0).ToArgb());
label1.ForeColor = c;
}
}
}
}
}

This line uses About 10 ms.
int retval = BitBlt(hDC, 0, 0, 1, 1, hSrcDC, location.X, location.Y, (int)CopyPixelOperation.SourceCopy);