| #!/usr/bin/perl |
| # |
| # Produce gamma-correction tables for alpha blending, assuming sRGB space. |
| # |
| |
| sub srgb_to_linear($) |
| { |
| my($s) = @_; |
| |
| if ($s <= 10) { |
| return $s/(255*12.92); |
| } else { |
| return (($s+14.025)/269.025)**2.4; |
| } |
| } |
| |
| sub linear_to_srgb($) |
| { |
| my($l) = @_; |
| my $s; |
| |
| if ($l <= 0.00304) { |
| $s = 12.92*$l; |
| } else { |
| $s = 1.055*$l**(1.0/2.4) - 0.055; |
| } |
| |
| return int($s*255+0.5); |
| } |
| |
| # Header |
| print "#include <inttypes.h>\n\n"; |
| |
| # |
| # Table 1: convert 8-bit sRGB values to 16-bit linear values |
| # |
| |
| print "const uint16_t __vesacon_srgb_to_linear[256] = {\n"; |
| for ($i = 0; $i <= 255; $i++) { |
| printf "\t%5d,\n", int(srgb_to_linear($i)*65535+0.5); |
| } |
| print "};\n\n"; |
| |
| # |
| # Table 2: convert linear values in the range [0, 65535*255], |
| # shifted right by 12 bits, to sRGB |
| # |
| |
| print "const uint8_t __vesacon_linear_to_srgb[4080] = {\n"; |
| for ($i = 0; $i <= 4079; $i++) { |
| printf "\t%3d,\n", linear_to_srgb(($i+0.5)/4079.937744); |
| } |
| print "};\n\n"; |