Resize transparent images using C#
- by MartinHN
Does anyone have the secret formula to resizing transparent images (mainly GIFs) without ANY quality loss - what so ever?
I've tried a bunch of stuff, the closest I get is not good enough.
Take a look at my main image:
http://www.thewallcompany.dk/test/main.gif
And then the scaled image:
http://www.thewallcompany.dk/test/ScaledImage.gif
//Internal resize for indexed colored images
void IndexedRezise(int xSize, int ySize)
{
BitmapData sourceData;
BitmapData targetData;
AdjustSizes(ref xSize, ref ySize);
scaledBitmap = new Bitmap(xSize, ySize, bitmap.PixelFormat);
scaledBitmap.Palette = bitmap.Palette;
sourceData = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height),
ImageLockMode.ReadOnly, bitmap.PixelFormat);
try
{
targetData = scaledBitmap.LockBits(new Rectangle(0, 0, xSize, ySize),
ImageLockMode.WriteOnly, scaledBitmap.PixelFormat);
try
{
xFactor = (Double)bitmap.Width / (Double)scaledBitmap.Width;
yFactor = (Double)bitmap.Height / (Double)scaledBitmap.Height;
sourceStride = sourceData.Stride;
sourceScan0 = sourceData.Scan0;
int targetStride = targetData.Stride;
System.IntPtr targetScan0 = targetData.Scan0;
unsafe
{
byte* p = (byte*)(void*)targetScan0;
int nOffset = targetStride - scaledBitmap.Width;
int nWidth = scaledBitmap.Width;
for (int y = 0; y < scaledBitmap.Height; ++y)
{
for (int x = 0; x < nWidth; ++x)
{
p[0] = GetSourceByteAt(x, y);
++p;
}
p += nOffset;
}
}
}
finally
{
scaledBitmap.UnlockBits(targetData);
}
}
finally
{
bitmap.UnlockBits(sourceData);
}
}
I'm using the above code, to do the indexed resizing.
Does anyone have improvement ideas?
