brooke/dither4
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This commit is contained in:
Brooke Vibber 2022-11-05 19:34:31 -07:00
parent 7867184985
commit 16c2caba95
1 changed files with 39 additions and 3 deletions
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42
dither4.js
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@ -1,3 +1,23 @@
function sRGBToLinear(val) {
let unit = val / 255;
if (unit < 0.04045) {
unit /= 12.92;
} else {
unit = ((unit + 0.055) / 1.055) ** 2.4;
}
return unit * 255;
}
function linearTosRGB(val) {
let unit = val / 255;
if (unit < 0.0031308) {
unit *= 12.92;
} else {
unit = 1.055 * unit ** (1 / 2.4) - 0.055;
}
return unit * 255;
}
class RGB { class RGB {
constructor(r, g, b) { constructor(r, g, b) {
this.r = r; this.r = r;
@ -12,6 +32,22 @@ class RGB {
return new RGB(r,g,b); return new RGB(r,g,b);
} }
sRGBToLinear() {
return new RGB(
sRGBToLinear(this.r),
sRGBToLinear(this.g),
sRGBToLinear(this.b)
);
}
linearTosRGB() {
return new RGB(
linearTosRGB(this.r),
linearTosRGB(this.g),
linearTosRGB(this.b)
);
}
cap() { cap() {
if (this.r < 0) { if (this.r < 0) {
this.r = 0; this.r = 0;
@ -321,7 +357,7 @@ let palette256 = [
0xf6e46f, 0xf6e46f,
0xfffa84, 0xfffa84,
0xffff99, 0xffff99,
].map((hex) => RGB.fromHex(hex)); ].map((hex) => RGB.fromHex(hex).sRGBToLinear());
function decimate(input, palette, n) { function decimate(input, palette, n) {
// to brute-force, the possible palettes are: // to brute-force, the possible palettes are:
@ -499,7 +535,7 @@ function convert(source, sink) {
(line[x * 4 + 0] + line[x * 4 + 4]) / 2, (line[x * 4 + 0] + line[x * 4 + 4]) / 2,
(line[x * 4 + 1] + line[x * 4 + 5]) / 2, (line[x * 4 + 1] + line[x * 4 + 5]) / 2,
(line[x * 4 + 2] + line[x * 4 + 6]) / 2 (line[x * 4 + 2] + line[x * 4 + 6]) / 2
); ).sRGBToLinear();
if (nextError) { if (nextError) {
rgb.r += nextError.red[i]; rgb.r += nextError.red[i];
rgb.g += nextError.green[i]; rgb.g += nextError.green[i];
@ -513,7 +549,7 @@ function convert(source, sink) {
nextError = error; nextError = error;
for (let x = 0; x < width; x++) { for (let x = 0; x < width; x++) {
let rgb = palette[output[x >> 1]]; let rgb = palette[output[x >> 1]].linearTosRGB();
line[x * 4 + 0] = rgb.r; line[x * 4 + 0] = rgb.r;
line[x * 4 + 1] = rgb.g; line[x * 4 + 1] = rgb.g;
line[x * 4 + 2] = rgb.b; line[x * 4 + 2] = rgb.b;