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Color to Monochrome conversion

See: Save a 32-bit Bitmap as 1-bit .bmp file in C#
Listing #1
public static Bitmap BitmapTo1Bpp(Bitmap source)
{
int Width = source.Width;
int Height = source.Height;
Bitmap dest = new Bitmap(Width, Height, PixelFormat.Format1bppIndexed);
BitmapData destBmpData = dest.LockBits(new Rectangle(0, 0, Width, Height), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed);
byte[] destBytes = new byte[(Width + 7) / 8];//19 bytes
for (int y = 0; y < Height; y++)
{
for (int x = 0; x < Width; x++)
{
Color c = source.GetPixel(x, y);
if (x % 8 == 0)
{
destBytes[x / 8] = 0;
}
if (c.GetBrightness() >= 0.5)
{
destBytes[x / 8] |= (byte)(0x80 >> (x % 8));
}
}
Marshal.Copy(destBytes, 0, (IntPtr)((long)destBmpData.Scan0 + destBmpData.Stride * y), destBytes.Length);
}
dest.UnlockBits(destBmpData);
return dest;
}
Listing #2
public static Bitmap BitmapTo1Bpp222(Bitmap source)
{
int Width = source.Width;
int Height = source.Height;
Bitmap dest = new Bitmap(Width, Height, PixelFormat.Format1bppIndexed);
BitmapData destBmpData = dest.LockBits(new Rectangle(0, 0, Width, Height), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed);
int destStride = destBmpData.Stride;
int destSize = Math.Abs(destStride) * Height;
byte[] destBytes = new byte[destSize];
for (int y = 0; y < Height; y++)
{
for (int x = 0; x < Width; x++)
{
Color c = source.GetPixel(x, y);
if (x % 8 == 0)
{
destBytes[x*y / 8] = 0;
}
if (c.GetBrightness() >= 0.5)
{
destBytes[x*y / 8] |= (byte)(0x80 >> (x % 8));
}
}
}
Marshal.Copy(destBytes, 0, destBmpData.Scan0, destBytes.Length);
dest.UnlockBits(destBmpData);
return dest;
}
See the position of Marshal.Copy().
Why does the Listing #1 work, but Listing #2 doesn't?
What modification can make the Listing #2 work?

Both of these are overly complicated. LockBits can convert data to 1bpp. Just open the source as 1bpp, copy its data into the new 1bpp image, and you're done.
I'm also quite baffled by the combination of GetPixel and LockBits. Usually, using LockBits means you realized that GetPixel is a horribly slow waste of time that performs a LockBits internally on every call.
public static Bitmap BitmapTo1Bpp(Bitmap source)
{
Rectangle rect = new Rectangle(0, 0, source.Width, source.Height);
Bitmap dest = new Bitmap(rect.Width, rect.Height, PixelFormat.Format1bppIndexed);
dest.SetResolution(source.HorizontalResolution, source.VerticalResolution);
BitmapData sourceData = source.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format1bppIndexed);
BitmapData targetData = dest.LockBits(rect, ImageLockMode.WriteOnly, PixelFormat.Format1bppIndexed);
Int32 actualDataWidth = (rect.Width + 7) / 8;
Int32 h = source.Height;
Int32 origStride = sourceData.Stride;
Int32 targetStride = targetData.Stride;
// buffer for one line of image data.
Byte[] imageData = new Byte[actualDataWidth];
Int64 sourcePos = sourceData.Scan0.ToInt64();
Int64 destPos = targetData.Scan0.ToInt64();
// Copy line by line, skipping by stride but copying actual data width
for (Int32 y = 0; y < h; y++)
{
Marshal.Copy(new IntPtr(sourcePos), imageData, 0, actualDataWidth);
Marshal.Copy(imageData, 0, new IntPtr(destPos), actualDataWidth);
sourcePos += origStride;
destPos += targetStride;
}
dest.UnlockBits(targetData);
source.UnlockBits(sourceData);
return dest;
}
Do note that conversion of data to indexed formats should be avoided in cases where your result is not 1bpp for pure black and white. Indexed formats are paletted, and doing it this way will not do any kind of reduction to an optimised palette approaching the image colours; it will just change the colours on the image to their closest match on the standard palette for this bit depth. For 1bpp this is just black and white, which is perfect, but for 4bpp and 8bpp it will give pretty bad results.
Also note that for some reason you can't convert from a higher to a lower indexed pixel format; it will throw an exception. Since you can convert a bitmap to 32-bit using the new Bitmap(Bitmap) constructor, this problem can easily be avoided by calling the code like this:
public static Bitmap ConvertTo1Bpp(Bitmap source)
{
PixelFormat sourcePf = source.PixelFormat;
if ((sourcePf & PixelFormat.Indexed) == 0 || Image.GetPixelFormatSize(sourcePf) == 1)
return BitmapTo1Bpp(source);
using (Bitmap bm32 = new Bitmap(source))
return BitmapTo1Bpp(bm32);
}

What is the most efficient way to loop through picture pixels

I've 2 images that I need to compare of 1280x800 each and I'm too worried about the efficiency as I'll have to do the same operations that include looping each second
I can think of so many ways to loop through a Bitmap object pixels but I don't know which would be more efficient, for now I am using simple for loop but it uses too much memory and processing which I could not afford at this point
Some tweaks here and there and all it does is less memory for more processing or the other way around
Any tips, information or experience is highly appreciated, I'm also open to use external libraries if they have much better efficiency.

from https://stackoverflow.com/a/6094092/1856345
Bitmap bmp = new Bitmap("SomeImage");
// Lock the bitmap's bits.
Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
BitmapData bmpData = bmp.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
// Get the address of the first line.
IntPtr ptr = bmpData.Scan0;
// Declare an array to hold the bytes of the bitmap.
int bytes = bmpData.Stride * bmp.Height;
byte[] rgbValues = new byte[bytes];
byte[] r = new byte[bytes / 3];
byte[] g = new byte[bytes / 3];
byte[] b = new byte[bytes / 3];
// Copy the RGB values into the array.
Marshal.Copy(ptr, rgbValues, 0, bytes);
int count = 0;
int stride = bmpData.Stride;
for (int column = 0; column < bmpData.Height; column++)
{
for (int row = 0; row < bmpData.Width; row++)
{
b[count] = rgbValues[(column * stride) + (row * 3)];
g[count] = rgbValues[(column * stride) + (row * 3) + 1];
r[count++] = rgbValues[(column * stride) + (row * 3) + 2];
}
}

Color to Bitmap

How do I go about setting a Bitmap with a Color of the pixels. I created a program with LockBits and it is very fast but now I need to set a PictureBox with that image I ran through the LockBits I do not want to use SetPixels My current code is:
Bitmap imageFile = new Bitmap(bmpPath);
BitmapData imageData = imageFile.LockBits(new Rectangle(0, 0, imageFile.Width, imageFile.Height), ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
IntPtr Pointer = imageData.Scan0;
int ArraySize = Math.Abs(imageData.Stride) * imageFile.Height;
byte[] PixelArray = new byte[ArraySize];
Marshal.Copy(Pointer, PixelArray, 0, ArraySize);
int PixelAmount = 4; //ArGb
Color ArGBformat;
Bitmap RenderedImage = new Bitmap(imageFile.Width, imageFile.Height);
byte NewAlpha;
byte NewRed;
byte NewGreen;
byte NewBlue;
unsafe
{
for (int y = 0; y < imageData.Height; y++)
{
byte* row = (byte*)imageData.Scan0 + (y * imageData.Stride);
for (int x = 0; x < imageData.Width; x++)
{
int offSet = x * PixelAmount;
// read pixels
byte blue = row[offSet];
byte green = row[offSet + 1];
byte red = row[offSet + 2];
byte alpha = row[offSet + 3];
//Manipulates pixels
NewAlpha = Convert.ToByte(Math.Abs(alpha - _Alpha));
NewRed = Convert.ToByte(Math.Abs(red - _Red));
NewBlue = Convert.ToByte(Math.Abs(blue - _Blue));
NewGreen = Convert.ToByte(Math.Abs(green - _Green));
ArGBformat = Color.FromArgb(NewAlpha, NewRed, NewGreen, NewBlue);
RenderedImage.SetPixel(x, y, ArGBformat); //Slow and want something else
}
}
}
I would like to set my PictureBox1 to the pixels that get ran through the program.

Found the answer. I needed to set the pixels back.
//Sets image
row[offSet] = NewBlue;
row[offSet + 1] = NewGreen;
row[offSet + 2] = NewRed;
row[offSet + 3] = NewAlpha;

How to split multipage Tiff using LibTiff.Net

In the LibTiff.Net documentation I've found that it is possible to get a specific page of the Tiff document.
But, if it is possible to split multipage Tiff (using LibTiff.Net) without knowing how many pages are there? How?
Using this example it returns only the first page.
Btw, the main problem is that Windows XP can't handle different tiff images, so I want to split it into jpeg ones.

//open tif file
var tif = Tiff.Open(#"file", "r");
//get number of pages
var num = tif.NumberOfDirectories();
for (short i = 0; i < num; i++)
{
//set current page
tif.SetDirectory(i);
Bitmap bmp = GetBitmapFormTiff(tif);
bmp.Save(string.Format(#"newfile{0}.bmp", i));
}
The code of GetBitmapFormTiff is from example:
private static Bitmap GetBitmapFormTiff(Tiff tif)
{
FieldValue[] value = tif.GetField(TiffTag.IMAGEWIDTH);
int width = value[0].ToInt();
value = tif.GetField(TiffTag.IMAGELENGTH);
int height = value[0].ToInt();
//Read the image into the memory buffer
var raster = new int[height * width];
if (!tif.ReadRGBAImage(width, height, raster))
{
return null;
}
var bmp = new Bitmap(width, height, PixelFormat.Format32bppRgb);
var rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
BitmapData bmpdata = bmp.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format32bppRgb);
var bits = new byte[bmpdata.Stride * bmpdata.Height];
for (int y = 0; y < bmp.Height; y++)
{
int rasterOffset = y * bmp.Width;
int bitsOffset = (bmp.Height - y - 1) * bmpdata.Stride;
for (int x = 0; x < bmp.Width; x++)
{
int rgba = raster[rasterOffset++];
bits[bitsOffset++] = (byte)((rgba >> 16) & 0xff);
bits[bitsOffset++] = (byte)((rgba >> 8) & 0xff);
bits[bitsOffset++] = (byte)(rgba & 0xff);
bits[bitsOffset++] = (byte)((rgba >> 24) & 0xff);
}
}
System.Runtime.InteropServices.Marshal.Copy(bits, 0, bmpdata.Scan0, bits.Length);
bmp.UnlockBits(bmpdata);
return bmp;
}

C# winforms code to c# wpf code

I have a drawing application developed in winforms C# which uses many System.Drawing.Bitmap object throughout the code.
Now I am writing it into WPF with c#. I have done almost 90% of the conversion.
Coming to the problem... I have the following code which is used to traverse the image pixel by pixel
Bitmap result = new Bitmap(img); // img is of System.Drawing.Image
result.SetResolution(img.HorizontalResolution, img.VerticalResolution);
BitmapData bmpData = result.LockBits(new Rectangle(0, 0, result.Width, result.Height), ImageLockMode.ReadWrite, img.PixelFormat);
int pixelBytes = System.Drawing.Image.GetPixelFormatSize(img.PixelFormat) / 8;
System.IntPtr ptr = bmpData.Scan0;
int size = bmpData.Stride * result.Height;
byte[] pixels = new byte[size];
int index = 0;
double R = 0;
double G = 0;
double B = 0;
System.Runtime.InteropServices.Marshal.Copy(ptr, pixels, 0, size);
for (int row = 0; row <= result.Height - 1; row++)
{
for (int col = 0; col <= result.Width - 1; col++)
{
index = (row * bmpData.Stride) + (col * pixelBytes);
R = pixels[index + 2];
G = pixels[index + 1];
B = pixels[index + 0];
.
.// logic code
.
}
}
result.UnlockBits(bmpData);
It uses System.Drawing's for the purpose.
Is it possible to achieve this thing in wpf as well keeping it simple as it is?

In addtion to Chris's anwser you might want to look at WriteableBitmap. It's another way to manipulate images pixels.
Example

You can use BitmapImage.CopyPixels to copy the image your pixel buffer.
BitmapImage img= new BitmapImage(...); // This is your image
int bytePerPixel = (img.Format.BitsPerPixel + 7) / 8;
int stride = img.PixelWidth * bytesPerPixel;
int size = img.PixelHeight * stride;
byte[] pixels = new byte[size];
img.CopyPixels(pixels, stride, 0);
// Now you can access 'pixels' to perform your logic
for (int row = 0; row < img.PixelHeight; row++)
{
for (int col = 0; col < img.PixelWidth; col++)
{
index = (row * stride) + (col * bytePerPixel );
...
}
}