public void compressImage(java.awt.image.BufferedImage image, DXTCompressionAttributes attributes,
java.nio.ByteBuffer buffer)
{
if (image == null)
{
String message = Logging.getMessage("nullValue.ImageIsNull");
Logging.logger().severe(message);
throw new ArgumentException(message);
}
if (attributes == null)
{
String message = Logging.getMessage("nullValue.AttributesIsNull");
Logging.logger().severe(message);
throw new ArgumentException(message);
}
if (buffer == null)
{
String message = Logging.getMessage("nullValue.BufferNull");
Logging.logger().severe(message);
throw new ArgumentException(message);
}
// If it is determined that the image and block have no alpha component, then we compress with DXT1 using a
// four color palette. Otherwise, we use the three color palette (with the fourth color as transparent black).
ColorBlock4x4 colorBlock = new ColorBlock4x4();
ColorBlockExtractor colorBlockExtractor = this.getColorBlockExtractor(image);
BlockDXT1 dxt1Block = new BlockDXT1();
BlockDXT1Compressor dxt1Compressor = new BlockDXT1Compressor();
int width = image.getWidth();
int height = image.getHeight();
bool imageHasAlpha = image.getColorModel().hasAlpha();
bool enableAlpha = attributes.isEnableDXT1Alpha();
int alphaThreshold = attributes.getDXT1AlphaThreshold();
for (int j = 0; j < height; j += 4)
{
for (int i = 0; i < width; i += 4)
{
colorBlockExtractor.extractColorBlock4x4(attributes, i, j, colorBlock);
if (enableAlpha && imageHasAlpha && blockHasDXT1Alpha(colorBlock, alphaThreshold))
{
dxt1Compressor.compressBlockDXT1a(colorBlock, attributes, dxt1Block);
}
else
{
dxt1Compressor.compressBlockDXT1(colorBlock, attributes, dxt1Block);
}
buffer.putShort((short)dxt1Block.color0);
buffer.putShort((short)dxt1Block.color1);
buffer.putInt((int)dxt1Block.colorIndexMask);
}
}
}
protected static long computePaletteIndices3(ColorBlock4x4 block, DXTCompressionAttributes attributes,
Color32[] palette)
{
// This implementation is based on code available in the nvidia-texture-tools project:
// http://code.google.com/p/nvidia-texture-tools/
//
// If the pixel alpha is below the specified threshold, we return index 3. In a three color DXT1 palette,
// index 3 is interpreted as transparent black. Otherwise, we compare the sums of absolute differences, and
// choose the nearest color index.
int alphaThreshold = attributes.getDXT1AlphaThreshold();
long mask = 0L;
long index;
for (int i = 0; i < 16; i++)
{
int d0 = colorDistanceSquared(palette[0], block.color[i]);
int d1 = colorDistanceSquared(palette[1], block.color[i]);
int d2 = colorDistanceSquared(palette[2], block.color[i]);
// TODO: implement bit twiddle as in computePaletteIndex4 to avoid conditional branching
if (block.color[i].a < alphaThreshold)
{
index = 3;
}
else if (d0 < d1 && d0 < d2)
{
index = 0;
}
else if (d1 < d2)
{
index = 1;
}
else
{
index = 2;
}
mask |= (index << (i << 1));
}
return(mask);
}