Function Png_Reconstruct

src/Bitmap.c:155–198

}

static void Png_Reconstruct(cc_uint8 type, cc_uint8 bytesPerPixel, cc_uint8* line, cc_uint8* prior, cc_uint32 lineLen) {
	cc_uint32 i, j;

	switch (type) {
	case PNG_FILTER_SUB:
		for (i = bytesPerPixel, j = 0; i < lineLen; i++, j++) {
			line[i] += line[j];
		}
		return;

	case PNG_FILTER_UP:
		for (i = 0; i < lineLen; i++) {
			line[i] += prior[i];
		}
		return;

	case PNG_FILTER_AVERAGE:
		for (i = 0; i < bytesPerPixel; i++) {
			line[i] += (prior[i] >> 1);
		}
		for (j = 0; i < lineLen; i++, j++) {
			line[i] += ((prior[i] + line[j]) >> 1);
		}
		return;

	case PNG_FILTER_PAETH:
		/* TODO: verify this is right */
		for (i = 0; i < bytesPerPixel; i++) {
			line[i] += prior[i];
		}
		for (j = 0; i < lineLen; i++, j++) {
			cc_uint8 a = line[j], b = prior[i], c = prior[j];
			int p = a + b - c;
			int pa = Math_AbsI(p - a);
			int pb = Math_AbsI(p - b);
			int pc = Math_AbsI(p - c);

			if (pa <= pb && pa <= pc) { line[i] += a; } 
			else if (pb <= pc) {        line[i] += b; } 
			else {                      line[i] += c; }
		}
		return;
	}
}

#define Bitmap_Set(dst, r,g,b,a) dst = BitmapCol_Make(r, g, b, a);