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Convert image to byte array C# in a proper way

My problem is that I need to convert an image to a byte array to obtain its pixels.
My image size is 268x188 and when I use the property PixelsFormat it returns Format24bppRgb, so I understand that each pixel contains 3 bytes.
If this is true, the size of the pixels should be 268*188*3 = 151152 bytes, but the byte array that I am creating has a size of 4906 bytes, which is the size of the image file in my computer.
I don´t know if there is another way to obtain these pixels or you can only obtain image file size.

If you want to ignore the header and the compression of the file you can do the following.
var path = ...
using(var image = Image.FromFile(path))
using(var bitmap = new Bitmap(image))
{
var bitmapData = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadOnly, bitmap.PixelFormat);
var bytesPerPixel = 4; // bitmapData.PixelFormat (image.PixelFormat and bitmapData.PixelFormat can be different)
var ptr = bitmapData.Scan0;
var imageSize = bitmapData.Width * bitmapData.Height * bytesPerPixel;
var data = new byte[imageSize];
for (int x = 0; x < imageSize; x += bytesPerPixel)
{
for(var y = 0; y < bytesPerPixel; y++)
{
data[x + y] = Marshal.ReadByte(ptr);
ptr += 1;
}
}
bitmap.UnlockBits(bitmapData);
}

To get image pixel try this:
public static byte[] GetImageRaw(Bitmap image)
{
if (image == null)
{
throw new ArgumentNullException(nameof(image));
}
if (image.PixelFormat != PixelFormat.Format24bppRgb)
{
throw new NotSupportedException("Invalid pixel format.");
}
const int PixelSize = 3;
var data = image.LockBits(
new Rectangle(Point.Empty, image.Size),
ImageLockMode.ReadWrite,
image.PixelFormat);
try
{
var bytes = new byte[data.Width * data.Height * PixelSize];
for (var y = 0; y < data.Height; ++y)
{
var source = (IntPtr)((long)data.Scan0 + y * data.Stride);
// copy row without padding
Marshal.Copy(source, bytes, y * data.Width * PixelSize, data.Width * PixelSize);
}
return bytes;
}
finally
{
image.UnlockBits(data);
}
}
Take a look at Bitmap.LockBits

I use this code in ASP.NET application. Very simple:
var imagePath = GetFilePathToYourImage();
using (var img = System.IO.File.OpenRead(imagePath))
{
var imageBytes = new byte[img.Length];
img.Read(imageBytes, 0, (int)img.Length);
}

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);
}

Convert RGB image to RGB 16-bit and 8-bit

I'm a newbie programmer.
Is there any algorithm to convert an image to 16-bit or 8-bit?
I didn't find it on google, I'am desperate.

Changing to 16 bit is the easier one. Assuming that the original image is in image, you can simply draw it into the result.
Bitmap result = new Bitmap(image.Width, image.Height, PixelFormat.Format16bppRgb565);
using (Graphics g = Graphics.FromImage(result))
{
g.DrawImage(image, 0, 0, image.Width, image.Height);
}
Unfortunately, this does not work for indexed images (images with palette, up to 256 colors). But you can find a solution in my answer here, see the ConvertPixelFormat method.

The only difference between 16 bit rgb and 8 bit rgb is the range, 16 bit has values form 0 to 65536 while 8 bit has values from 0 to 256, hence you should just be able to devide a 16 bit rgb value by 256 using integer division (for simplicity) and that will be it converted. (You need to decide the value in each plane by 256)

Convert RGB image to 8-bit
public static Bitmap ConvertFromRGBTo8bit(this Bitmap rgbBmp)
{
// Copy image to byte Array
var BoundsRectSrc = new Rectangle(0, 0, rgbBmp.Width, rgbBmp.Height);
BitmapData bmpDataSrc = rgbBmp.LockBits(BoundsRectSrc, ImageLockMode.WriteOnly, rgbBmp.PixelFormat);
IntPtr ptrSrc = bmpDataSrc.Scan0;
int imgSizeSrc = bmpDataSrc.Stride * rgbBmp.Height;
byte[] rgbValues = new byte[imgSizeSrc];
Marshal.Copy(ptrSrc, rgbValues, 0, imgSizeSrc);
// Crearte bitmap with 8 index grayscale
Bitmap newBmp = new Bitmap(rgbBmp.Width, rgbBmp.Height, PixelFormat.Format8bppIndexed);
ColorPalette ncp = newBmp.Palette;
for (int i = 0; i < 256; i++)
ncp.Entries[i] = Color.FromArgb(255, i, i, i);
newBmp.Palette = ncp;
var BoundsRectDst = new Rectangle(0, 0, rgbBmp.Width, rgbBmp.Height);
BitmapData bmpDataDst = newBmp.LockBits(BoundsRectDst, ImageLockMode.WriteOnly, newBmp.PixelFormat);
IntPtr ptrDst = bmpDataDst.Scan0;
int imgSizeDst = bmpDataDst.Stride * newBmp.Height;
byte[] grayValues = new byte[imgSizeDst];
// Convert image to 8 bit according average pixel
if (rgbBmp.PixelFormat == PixelFormat.Format16bppRgb555 || rgbBmp.PixelFormat == PixelFormat.Format16bppRgb565)
for (int i = 0, j = 0; i < grayValues.Length; i++, j += 2)
grayValues[i] = (byte)((rgbValues[j] + rgbValues[j + 1]) / 2);
else if (rgbBmp.PixelFormat == PixelFormat.Format24bppRgb)
for (int i = 0, j = 0; i < grayValues.Length; i++, j += 3)
grayValues[i] = (byte)((rgbValues[j] + rgbValues[j + 1] + rgbValues[j + 2]) / 3);
else if (rgbBmp.PixelFormat == PixelFormat.Format32bppRgb)
for (int i = 0, j = 0; i < grayValues.Length; i++, j += 4)
grayValues[i] = (byte)((rgbValues[j] + rgbValues[j + 1] + rgbValues[j + 2] + rgbValues[j + 3]) / 4);
Marshal.Copy(grayValues, 0, ptrDst, imgSizeDst);
newBmp.UnlockBits(bmpDataDst);
rgbBmp.UnlockBits(bmpDataSrc);
return newBmp;
}

Sharpdx load bitmap fom file Windows 8 apps

I've found this example in SharpDX "BitmapApp" samples:
public static Bitmap LoadFromFile(RenderTarget renderTarget, string file)
{
// Loads from file using System.Drawing.Image
using (var bitmap = (System.Drawing.Bitmap)System.Drawing.Image.FromFile(file))
{
var sourceArea = new System.Drawing.Rectangle(0, 0, bitmap.Width, bitmap.Height);
var bitmapProperties = new BitmapProperties(new PixelFormat(Format.R8G8B8A8_UNorm, AlphaMode.Premultiplied));
var size = new Size2(bitmap.Width, bitmap.Height);
// Transform pixels from BGRA to RGBA
int stride = bitmap.Width * sizeof(int);
using (var tempStream = new DataStream(bitmap.Height * stride, true, true))
{
// Lock System.Drawing.Bitmap
var bitmapData = bitmap.LockBits(sourceArea, ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppPArgb);
// Convert all pixels
for (int y = 0; y < bitmap.Height; y++)
{
int offset = bitmapData.Stride*y;
for (int x = 0; x < bitmap.Width; x++)
{
// Not optimized
byte B = Marshal.ReadByte(bitmapData.Scan0, offset++);
byte G = Marshal.ReadByte(bitmapData.Scan0, offset++);
byte R = Marshal.ReadByte(bitmapData.Scan0, offset++);
byte A = Marshal.ReadByte(bitmapData.Scan0, offset++);
int rgba = R | (G << 8) | (B << 16) | (A << 24);
tempStream.Write(rgba);
}
}
bitmap.UnlockBits(bitmapData);
tempStream.Position = 0;
return new Bitmap(renderTarget, size, tempStream, stride, bitmapProperties);
}
}
}
But my problem is that only works for wpf or deskop application.
I want to build a Windows Store app but System.Drawing doesn't exist any longer.
It has been replaced by Windows.Graphics.Imaging (Replacement of System.drawing in developing windows 8 apps)
I'm a beginner and I dont know how to make this function works with windows 8.
This function was perfect for me because I want to load a .png file and then I want to transform it. I tried and it works in the BitmappApp samples.
RenderTarget2D.Transform = Matrix.Transformation2D(center, 0f, new Vector2(500 / _bitmap.Size.Width, 900 / _bitmap.Size.Height), center, 0f,Vector2.Zero);
RenderTarget2D.DrawBitmap(_bitmap, 1.0f, BitmapInterpolationMode.Linear);

libtiff.net writeScanLine returns false

I'm using libtiff.net to make a tiff from a jpeg.
The problem apears when I try to write, because the tiff.writeScanLine returns false, meaning the image isn't written in the tiff.
Why is this happening? And how can I figure out what's wrong?
Here's the code:
private bool creatingTiff()
{
using (Bitmap bmp = new Bitmap(targetFile))
{
using (Tiff tif = Tiff.Open("BitmapTo24BitColorTiff.tif", "w"))
{
byte[] raster = getImageRasterBytes(bmp, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
tif.SetField(TiffTag.IMAGEWIDTH, bmp.Width);
tif.SetField(TiffTag.IMAGELENGTH, bmp.Height);
tif.SetField(TiffTag.COMPRESSION, Compression.OJPEG);
tif.SetField(TiffTag.PHOTOMETRIC, Photometric.YCBCR);
tif.SetField(TiffTag.SUBFILETYPE, 0);
tif.SetField(TiffTag.ROWSPERSTRIP, bmp.Height);
tif.SetField(TiffTag.ORIENTATION, BitMiracle.LibTiff.Classic.Orientation.TOPLEFT);
tif.SetField(TiffTag.XRESOLUTION, bmp.HorizontalResolution);
tif.SetField(TiffTag.YRESOLUTION, bmp.VerticalResolution);
tif.SetField(TiffTag.RESOLUTIONUNIT, ResUnit.INCH);
tif.SetField(TiffTag.BITSPERSAMPLE, 8);
tif.SetField(TiffTag.SAMPLESPERPIXEL, 3);
tif.SetField(TiffTag.JPEGIFOFFSET, 768);
tif.SetField(TiffTag.PLANARCONFIG, PlanarConfig.CONTIG);
for (int i = 0, offset = 0; i < bmp.Height; i++)
{
bool b = tif.WriteScanline(raster, offset, i, 0);
Console.WriteLine("write succes: " + b);
offset += stride;
}
}
System.Diagnostics.Process.Start("BitmapTo24BitColorTiff.tif");
return true;
}
}
private static byte[] getImageRasterBytes(Bitmap bmp, System.Drawing.Imaging.PixelFormat format)
{
System.Drawing.Rectangle rect = new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height);
byte[] bits = null;
try
{
// Lock the managed memory
BitmapData bmpdata = bmp.LockBits(rect, ImageLockMode.ReadWrite, format);
// Declare an array to hold the bytes of the bitmap.
bits = new byte[bmpdata.Stride * bmpdata.Height];
// Copy the values into the array.
System.Runtime.InteropServices.Marshal.Copy(bmpdata.Scan0, bits, 0, bits.Length);
// Release managed memory
bmp.UnlockBits(bmpdata);
}
catch
{
return null;
}
return bits;
}
private static void convertSamples(byte[] data, int width, int height)
{
int stride = data.Length / height;
const int samplesPerPixel = 3;
for (int y = 0; y < height; y++)
{
int offset = stride * y;
int strideEnd = offset + width * samplesPerPixel;
for (int i = offset; i < strideEnd; i += samplesPerPixel)
{
byte temp = data[i + 2];
data[i + 2] = data[i];
data[i] = temp;
}
}
}
The tif-tags are written, but the image itself isn't. Perhaps if someone can point me in the direction of the library developers blog (BitMiracle), I can direct my problem to them directly.

I think your code has the following errors:
You can not use Compression.OJPEG for new images. Old-JPEGs can only be de-compressed.
You probably should not specify TiffTag.JPEGIFOFFSET value by hand. The library will specify proper value itself.
You are trying to write the whole strip using WriteScanline method. You should use WriteEncodedStrip instead.
It also helps to review warnings emitted by the library (it emits them into console).