// create image and load external data
imgSrc = vgCreateImage(VG_lRGBA_8888, imgGirlAlphaWidth, imgGirlAlphaHeight, VG_IMAGE_QUALITY_NONANTIALIASED);
vgImageSubData(imgSrc, (const void *)imgGirlAlphaData, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
imgDst = vgCreateImage(VG_lRGBA_8888, imgGirlAlphaWidth, imgGirlAlphaHeight, VG_IMAGE_QUALITY_NONANTIALIASED);

// set channel masks
vgSeti(VG_FILTER_CHANNEL_MASK, VG_RED | VG_GREEN | VG_BLUE | VG_ALPHA);
vgSeti(VG_FILTER_FORMAT_LINEAR, VG_TRUE);
vgSeti(VG_FILTER_FORMAT_PREMULTIPLIED, VG_FALSE);

// generate a non-premultiplied palatte
for (i = 0; i < 256; ++i) {
	redLUT[i] = (VGubyte)(127.0f * cos(2 * (i * 6.2831f / 256.0f)) + 127.5f);
	greenLUT[i] = (VGubyte)(127.0f * cos(1 * (i * 6.2831f / 256.0f)) + 127.5f);
	blueLUT[i] = (VGubyte)(127.0f * sin(3 * (i * 6.2831f / 256.0f)) + 127.5f);
	alphaLUT[i] = i;
}

// lookup filter, in linear non-premultiplied color space
vgLookup(imgDst, imgSrc, redLUT, greenLUT, blueLUT, alphaLUT, VG_TRUE, VG_FALSE);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_lookup_l.png");
saveImage32(f, imgFileName, "Lookup filter, in linear non-premultiplied color space.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

// lookup filter, in non-linear non-premultiplied color space
vgLookup(imgDst, imgSrc, redLUT, greenLUT, blueLUT, alphaLUT, VG_FALSE, VG_FALSE);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_lookup_s.png");
saveImage32(f, imgFileName, "Lookup filter, in non-linear non-premultiplied color space.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);


// generate a premultiplied palatte
for (i = 0; i < 256; ++i) {
	alphaLUT[i] = i;
	redLUT[i] = (VGubyte)(alphaLUT[i] * (127.0f * cos(2 * (i * 6.2831f / 256.0f)) + 127.5f) / 255.0f);
	greenLUT[i] = (VGubyte)(alphaLUT[i] * (127.0f * cos(1 * (i * 6.2831f / 256.0f)) + 127.5f) / 255.0f);
	blueLUT[i] = (VGubyte)(alphaLUT[i] * (127.0f * sin(3 * (i * 6.2831f / 256.0f)) + 127.5f) / 255.0f);
}

// lookup filter, in linear premultiplied color space
vgLookup(imgDst, imgSrc, redLUT, greenLUT, blueLUT, alphaLUT, VG_TRUE, VG_TRUE);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_lookup_lpre.png");
saveImage32(f, imgFileName, "Lookup filter, in linear non-premultiplied color space.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

// lookup filter, in non-linear premultiplied color space
vgLookup(imgDst, imgSrc, redLUT, greenLUT, blueLUT, alphaLUT, VG_FALSE, VG_TRUE);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_lookup_spre.png");
saveImage32(f, imgFileName, "Lookup filter, in non-linear non-premultiplied color space.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

vgDestroyImage(imgSrc);
vgDestroyImage(imgDst);