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