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dither.js
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// The standard 4x4 (64 pixel) dithering matrix
var dither = [
[0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0],
[1, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0],
[1, 0, 0, 0,
0, 0, 0, 0,
0, 0, 1, 0,
0, 0, 0, 0],
[1, 0, 1, 0,
0, 0, 0, 0,
0, 0, 1, 0,
0, 0, 0, 0],
[1, 0, 1, 0,
0, 0, 0, 0,
1, 0, 1, 0,
0, 0, 0, 0],
[1, 0, 1, 0,
0, 1, 0, 0,
1, 0, 1, 0,
0, 0, 0, 0],
[1, 0, 1, 0,
0, 1, 0, 0,
1, 0, 1, 0,
0, 0, 0, 1],
[1, 0, 1, 0,
0, 1, 0, 1,
1, 0, 1, 0,
0, 0, 0, 1],
[1, 0, 1, 0,
0, 1, 0, 1,
1, 0, 1, 0,
0, 1, 0, 1],
[1, 1, 1, 0,
0, 1, 0, 1,
1, 0, 1, 0,
0, 1, 0, 1],
[1, 1, 1, 0,
0, 1, 0, 1,
1, 0, 1, 1,
0, 1, 0, 1],
[1, 1, 1, 1,
0, 1, 0, 1,
1, 0, 1, 1,
0, 1, 0, 1],
[1, 1, 1, 1,
0, 1, 0, 1,
1, 1, 1, 1,
0, 1, 0, 1],
[1, 1, 1, 1,
1, 1, 0, 1,
1, 1, 1, 1,
0, 1, 0, 1],
[1, 1, 1, 1,
1, 1, 0, 1,
1, 1, 1, 1,
0, 1, 1, 1],
[1, 1, 1, 1,
1, 1, 1, 1,
1, 1, 1, 1,
0, 1, 1, 1],
[1, 1, 1, 1,
1, 1, 1, 1,
1, 1, 1, 1,
1, 1, 1, 1]
];
// Get the state of any coordinate from a dithering matrix
function getDither(matrix, x, y) {
return matrix[((y % 4) * 4) + (x % 4)];
}
// Gets the color in the palette which best matches the given color
function bestMatch(palette, color) {
var best = [Infinity, [0, 0, 0]];
for (var i = 0; i < palette.length; i += 1) {
var difference = Math.abs(palette[i][0] - color[0]) + Math.abs(palette[i][1] - color[1]) + Math.abs(palette[i][2] - color[2]);
if (difference < best[0]) {
best = [difference, palette[i]];
}
}
return best[1];
}
// Same as above, except excluding the color in the palette at the specified index
function bestMatchEx(palette, color, index) {
var best = [Infinity, [0, 0, 0]];
for (var i = 0; i < palette.length; i += 1) {
if (i == index) {continue;}
var difference = Math.abs(palette[i][0] - color[0]) + Math.abs(palette[i][1] - color[1]) + Math.abs(palette[i][2] - color[2]);
if (difference < best[0]) {
best = [difference, palette[i]];
}
}
return best[1];
}
// Divides all components of a color by a given factor
function divideColor(color, factor) {
return [color[0] / factor, color[1] / factor, color[2] / factor];
}
// Multiplies all components of a color by a given factor
function multiplyColor(color, factor) {
return [color[0] * factor, color[1] * factor, color[2] * factor];
}
// Adds two colors together by adding their components
function addColor(a, b) {
return [a[0] + b[0], a[1] + b[1], a[2] + b[2]];
}