Contents

#include "oily_png_ext.h"

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);
}

VALUE oily_png_color_compose_quick(VALUE self, VALUE fg_color, VALUE bg_color) {
  return UINT2NUM(oily_png_compose_color(NUM2UINT(fg_color), NUM2UINT(bg_color)));
}

Version data entries

4 entries across 4 versions & 1 rubygems

Version	Path
oily_png-1.0.1	ext/oily_png/color.c
oily_png-1.0.0	ext/oily_png/color.c
oily_png-1.0.0.rc2	ext/oily_png/color.c
oily_png-1.0.0.rc1	ext/oily_png/color.c