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

问题:

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.

回答1:

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.

回答2:

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)

回答3:

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; } 

文章来源: Convert RGB image to RGB 16-bit and 8-bit