// 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);

// create a 5x5 kernel matrix
kernel[0] = -5;  kernel[5] = -3;  kernel[10] = -2;  kernel[15] = 0;  kernel[20] = 0;
kernel[1] = -3;  kernel[6] = -2;  kernel[11] = -1;  kernel[16] = 0;  kernel[21] = 0;
kernel[2] = -2;  kernel[7] = -1;  kernel[12] =  1;  kernel[17] = 1;  kernel[22] = 2;
kernel[3] =  0;  kernel[8] =  0;  kernel[13] =  1;  kernel[18] = 2;  kernel[23] = 3;
kernel[4] =  0;  kernel[9] =  0;  kernel[14] =  2;  kernel[19] = 3;  kernel[24] = 5;

// set channel masks and a border color
vgSeti(VG_FILTER_CHANNEL_MASK, VG_RED | VG_GREEN | VG_BLUE | VG_ALPHA);
col[0] = 0.12f;
col[1] = 0.35f;
col[2] = 0.75f;
col[3] = 1.0f;
vgSetfv(VG_TILE_FILL_COLOR, 4, col);
vgSeti(VG_FILTER_FORMAT_LINEAR, VG_TRUE);
vgSeti(VG_FILTER_FORMAT_PREMULTIPLIED, VG_FALSE);

// basic centered convolve filter
vgConvolve(imgDst, imgSrc, 5, 5, 2, 2, kernel, 1.0f / 1.0f, 0.0f, VG_TILE_FILL);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_convolve.png");
saveImage32(f, imgFileName, "Basic centered convolve filter.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

// decentered convolve filter, with tile fill
vgConvolve(imgDst, imgSrc, 5, 5, 128, -128, kernel, 1.0f / 1.0f, 0.0f, VG_TILE_FILL);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_convolve_fill.png");
saveImage32(f, imgFileName, "Decentered convolve filter, with tile fill.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

// decentered convolve filter, with tile pad
vgConvolve(imgDst, imgSrc, 5, 5, 128, -128, kernel, 1.0f / 1.0f, 0.0f, VG_TILE_PAD);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_convolve_pad.png");
saveImage32(f, imgFileName, "Decentered convolve filter, with tile pad.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

// decentered convolve filter, with tile repeat
vgConvolve(imgDst, imgSrc, 5, 5, 128, -128, kernel, 1.0f / 1.0f, 0.0f, VG_TILE_REPEAT);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_convolve_repeat.png");
saveImage32(f, imgFileName, "Decentered convolve filter, with tile repeat.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

// decentered convolve filter, with tile reflect
vgConvolve(imgDst, imgSrc, 5, 5, 128, -128, kernel, 1.0f / 1.0f, 0.0f, VG_TILE_REFLECT);
vgGetImageSubData(imgDst, imgOutputDataRGBA, imgGirlAlphaDataStride, imgGirlAlphaFormat, 0, 0, imgGirlAlphaWidth, imgGirlAlphaHeight);
strcpy(imgFileName, "filter_convolve_reflect.png");
saveImage32(f, imgFileName, "Decentered convolve filter, with tile reflect.", imgGirlAlphaWidth, imgGirlAlphaHeight, imgOutputDataRGBA, 0);

vgDestroyImage(imgSrc);
vgDestroyImage(imgDst);