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private static ColorPalette _Palette = null;
private static ColorPalette m_Palette
{
get
{
if (_Palette == null)
{
_Palette = new Bitmap(1, 1, PixelFormat.Format8bppIndexed).Palette;
for (int i = 0; i < 256; i++)
{
_Palette.Entries[i] = Color.FromArgb(i, i, i);
}
}
return _Palette;
}
}
public static Bitmap Convert(Bitmap pImage, PixelFormat pFormat)
{
switch (pFormat)
{
case PixelFormat.Format8bppIndexed:
{
int w = pImage.Width, h = pImage.Height, r, ic, oc, bmpStride, outputStride, bytesPerPixel;
PixelFormat pfIn = pImage.PixelFormat;
Bitmap output;
BitmapData bmpData, outputData;
//Create the new bitmap
output = new Bitmap(w, h, PixelFormat.Format8bppIndexed);
output.Palette = m_Palette;
//No need to convert formats if already in 8 bit
if (pfIn == PixelFormat.Format8bppIndexed)
{
output = (Bitmap)pImage.Clone();
//Make sure the palette is a grayscale palette and not some other
//8-bit indexed palette
output.Palette = m_Palette;
return output;
}
//Get the number of bytes per pixel
switch (pfIn)
{
case PixelFormat.Format24bppRgb: bytesPerPixel = 3; break;
case PixelFormat.Format32bppArgb: bytesPerPixel = 4; break;
case PixelFormat.Format32bppRgb: bytesPerPixel = 4; break;
default: throw new InvalidOperationException("Image format not supported");
}
//Lock the images
bmpData = pImage.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, pfIn);
outputData = output.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed);
bmpStride = bmpData.Stride;
outputStride = outputData.Stride;
//Traverse each pixel of the image
unsafe
{
byte* bmpPtr = (byte*)bmpData.Scan0.ToPointer(),
outputPtr = (byte*)outputData.Scan0.ToPointer();
if (bytesPerPixel == 3)
{
//Convert the pixel to it's luminance using the formula:
// L = .299*R + .587*G + .114*B
//Note that ic is the input column and oc is the output column
for (r = 0; r < h; r++)
for (ic = oc = 0; oc < w; ic += 3, ++oc)
outputPtr[r * outputStride + oc] = (byte)(int)
(0.299f * bmpPtr[r * bmpStride + ic] +
0.587f * bmpPtr[r * bmpStride + ic + 1] +
0.114f * bmpPtr[r * bmpStride + ic + 2]);
}
else //bytesPerPixel == 4
{
//Convert the pixel to it's luminance using the formula:
// L = alpha * (.299*R + .587*G + .114*B)
//Note that ic is the input column and oc is the output column
for (r = 0; r < h; r++)
for (ic = oc = 0; oc < w; ic += 4, ++oc)
outputPtr[r * outputStride + oc] = (byte)(int)
((bmpPtr[r * bmpStride + ic] / 255.0f) *
(0.299f * bmpPtr[r * bmpStride + ic + 1] +
0.587f * bmpPtr[r * bmpStride + ic + 2] +
0.114f * bmpPtr[r * bmpStride + ic + 3]));
}
}
//Unlock the images
pImage.UnlockBits(bmpData);
output.UnlockBits(outputData);
return output;
}
default:
{
var output = new Bitmap(pImage.Width, pImage.Height, pFormat);
using (Graphics g = Graphics.FromImage(output))
{
g.DrawImage(pImage, new Point(0, 0));
}
return output;
}
}
} |
Image Processing - Step 1
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