private boolean needToCreateIndex(RenderedImage image) {
SampleModel sampleModel = image.getSampleModel();
ColorModel colorModel = image.getColorModel();
return sampleModel.getNumBands() != 1
|| sampleModel.getSampleSize()[0] > 8
|| colorModel.getComponentSize()[0] > 8;
}
/** Create a color table from the image ColorModel and SampleModel. */
private static byte[] createColorTable(ColorModel colorModel, SampleModel sampleModel) {
byte[] colorTable;
if (colorModel instanceof IndexColorModel) {
IndexColorModel icm = (IndexColorModel) colorModel;
int mapSize = icm.getMapSize();
/**
* The GIF image format assumes that size of image palette is power of two. We will use
* closest larger power of two as size of color table.
*/
int ctSize = getGifPaletteSize(mapSize);
byte[] reds = new byte[ctSize];
byte[] greens = new byte[ctSize];
byte[] blues = new byte[ctSize];
icm.getReds(reds);
icm.getGreens(greens);
icm.getBlues(blues);
/**
* fill tail of color component arrays by replica of first color in order to avoid appearance
* of extra colors in the color table
*/
for (int i = mapSize; i < ctSize; i++) {
reds[i] = reds[0];
greens[i] = greens[0];
blues[i] = blues[0];
}
colorTable = new byte[3 * ctSize];
int idx = 0;
for (int i = 0; i < ctSize; i++) {
colorTable[idx++] = reds[i];
colorTable[idx++] = greens[i];
colorTable[idx++] = blues[i];
}
} else if (sampleModel.getNumBands() == 1) {
// create gray-scaled color table for single-banded images
int numBits = sampleModel.getSampleSize()[0];
if (numBits > 8) {
numBits = 8;
}
int colorTableLength = 3 * (1 << numBits);
colorTable = new byte[colorTableLength];
for (int i = 0; i < colorTableLength; i++) {
colorTable[i] = (byte) (i / 3);
}
} else {
// We do not have enough information here
// to create well-fit color table for RGB image.
colorTable = null;
}
return colorTable;
}
