izapple2/screenNtscFilter.go

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package apple2
import (
"image"
"image/color"
)
func getNTSCColorMap() []color.Color {
// RGB values from https://mrob.com/pub/xapple2/colors.html
black := color.RGBA{0, 0, 0, 255} /*COLOR=0 */ /* 0 0 0*/
dkBlue := color.RGBA{96, 78, 189, 255} /*COLOR=2 */ /* 0 60 25*/
red := color.RGBA{227, 30, 96, 255} /*COLOR=1 */ /* 90 60 25*/
brown := color.RGBA{96, 114, 3, 255} /*COLOR=8 */ /*180 60 25*/
dkGreen := color.RGBA{0, 163, 96, 255} /*COLOR=4 */ /*270 60 25*/
grey := color.RGBA{156, 156, 156, 255} /*COLOR=10*/ /* 0 0 50*/
purple := color.RGBA{255, 68, 253, 255} /*HCOLOR=2*/ /* 45 100 50*/
orange := color.RGBA{255, 106, 60, 255} /*HCOLOR=5*/ /*135 100 50*/
green := color.RGBA{20, 245, 60, 255} /*HCOLOR=1*/ /*225 100 50*/
blue := color.RGBA{20, 207, 253, 255} /*HCOLOR=6*/ /*315 100 50*/
//purple := color.RGBA{255, 68, 253, 255} /*COLOR=3 */ /* 45 100 50*/
//orange := color.RGBA{255, 106, 60, 255} /*COLOR=9 */ /*135 100 50*/
//green := color.RGBA{20, 245, 60, 255} /*COLOR=12*/ /*225 100 50*/
//blue := color.RGBA{20, 207, 253, 255} /*COLOR=6 */ /*315 100 50*/
ltBlue := color.RGBA{208, 195, 255, 255} /*COLOR=7 */ /* 0 60 75*/
pink := color.RGBA{255, 160, 208, 255} /*COLOR=11*/ /* 90 60 75*/
yellow := color.RGBA{208, 221, 141, 255} /*COLOR=13*/ /*180 60 75*/
aqua := color.RGBA{114, 255, 208, 255} /*COLOR=14*/ /*270 60 75*/
white := color.RGBA{255, 255, 255, 255} /*COLOR=15*/ /* 0 0 100*/
colorMap := []color.Color{
/* 0000 */ black,
/* 0001 */ brown,
/* 0010 */ dkGreen,
/* 0011 */ green,
/* 0100 */ dkBlue,
/* 0101 */ grey,
/* 0110 */ blue,
/* 0111 */ aqua,
/* 1000 */ red,
/* 1001 */ orange,
/* 1010 */ grey,
/* 1011 */ yellow,
/* 1100 */ purple,
/* 1101 */ pink,
/* 1110 */ ltBlue,
/* 1111 */ white,
}
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return colorMap
}
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func filterNTSCColor(blacker bool, in *image.RGBA) *image.RGBA {
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colorMap := getNTSCColorMap()
b := in.Bounds()
size := image.Rect(0, 0, b.Dx()+3, b.Dy())
out := image.NewRGBA(size)
for y := b.Min.Y; y < b.Max.Y; y++ {
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// We store the last four bits. We start with 0000
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v := 0
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for x := b.Min.X; x < b.Dx(); x++ {
cIn := in.At(x, y)
r, _, _, _ := cIn.RGBA()
pos := 1 << (3 - uint(x%4))
var cOut color.Color
if r != 0 {
v |= pos
cOut = colorMap[v]
} else {
v &^= pos
if blacker {
// If there is no luminance, let's have black anyway
cOut = colorMap[0]
} else {
cOut = colorMap[v]
}
}
out.Set(x, y, cOut)
}
// We fade for the last three positions
for x := b.Dx(); x < b.Max.X; x++ {
v = (v << 1) & 0xF
cOut := colorMap[v]
out.Set(x, y, cOut)
}
}
return out
}