PIXEL oily_png_color_interpolate_quick(PIXEL fg, PIXEL bg, int alpha) {
BYTE a_com, new_r, new_g, new_b, new_a;
if (alpha >= 255) return fg;
if (alpha <= 0) return bg;
a_com = 255 - alpha;
new_r = INT8_MULTIPLY(alpha, R_BYTE(fg)) + INT8_MULTIPLY(a_com, R_BYTE(bg));
new_g = INT8_MULTIPLY(alpha, G_BYTE(fg)) + INT8_MULTIPLY(a_com, G_BYTE(bg));
new_b = INT8_MULTIPLY(alpha, B_BYTE(fg)) + INT8_MULTIPLY(a_com, B_BYTE(bg));
new_a = INT8_MULTIPLY(alpha, A_BYTE(fg)) + INT8_MULTIPLY(a_com, A_BYTE(bg));
return BUILD_PIXEL(new_r, new_g, new_b, new_a);
}
PIXEL oily_png_compose_color(PIXEL fg, PIXEL bg) {
// Check for simple cases first
if ((A_BYTE(fg) == 0xff) || (A_BYTE(bg) == 0x00)) return fg;
if (A_BYTE(fg) == 0x00) return bg;
// Calculate the new values using fast 8-bit multiplication
BYTE a_com = INT8_MULTIPLY(0xff - A_BYTE(fg), A_BYTE(bg));
BYTE new_r = INT8_MULTIPLY(A_BYTE(fg), R_BYTE(fg)) + INT8_MULTIPLY(a_com, R_BYTE(bg));
BYTE new_g = INT8_MULTIPLY(A_BYTE(fg), G_BYTE(fg)) + INT8_MULTIPLY(a_com, G_BYTE(bg));
BYTE new_b = INT8_MULTIPLY(A_BYTE(fg), B_BYTE(fg)) + INT8_MULTIPLY(a_com, B_BYTE(bg));
BYTE new_a = A_BYTE(fg) + a_com;
return BUILD_PIXEL(new_r, new_g, new_b, new_a);
}
