94 lines
2.3 KiB
JavaScript
94 lines
2.3 KiB
JavaScript
"use strict";
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function dePalette(indata, outdata, width, height, palette) {
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let pxPos = 0;
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// use values from palette
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for (let y = 0; y < height; y++) {
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for (let x = 0; x < width; x++) {
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let color = palette[indata[pxPos]];
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if (!color) {
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throw new Error("index " + indata[pxPos] + " not in palette");
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}
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for (let i = 0; i < 4; i++) {
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outdata[pxPos + i] = color[i];
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}
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pxPos += 4;
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}
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}
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}
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function replaceTransparentColor(indata, outdata, width, height, transColor) {
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let pxPos = 0;
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for (let y = 0; y < height; y++) {
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for (let x = 0; x < width; x++) {
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let makeTrans = false;
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if (transColor.length === 1) {
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if (transColor[0] === indata[pxPos]) {
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makeTrans = true;
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}
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} else if (
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transColor[0] === indata[pxPos] &&
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transColor[1] === indata[pxPos + 1] &&
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transColor[2] === indata[pxPos + 2]
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) {
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makeTrans = true;
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}
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if (makeTrans) {
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for (let i = 0; i < 4; i++) {
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outdata[pxPos + i] = 0;
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}
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}
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pxPos += 4;
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}
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}
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}
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function scaleDepth(indata, outdata, width, height, depth) {
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let maxOutSample = 255;
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let maxInSample = Math.pow(2, depth) - 1;
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let pxPos = 0;
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for (let y = 0; y < height; y++) {
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for (let x = 0; x < width; x++) {
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for (let i = 0; i < 4; i++) {
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outdata[pxPos + i] = Math.floor(
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(indata[pxPos + i] * maxOutSample) / maxInSample + 0.5
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);
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}
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pxPos += 4;
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}
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}
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}
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module.exports = function (indata, imageData) {
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let depth = imageData.depth;
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let width = imageData.width;
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let height = imageData.height;
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let colorType = imageData.colorType;
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let transColor = imageData.transColor;
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let palette = imageData.palette;
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let outdata = indata; // only different for 16 bits
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if (colorType === 3) {
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// paletted
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dePalette(indata, outdata, width, height, palette);
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} else {
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if (transColor) {
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replaceTransparentColor(indata, outdata, width, height, transColor);
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}
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// if it needs scaling
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if (depth !== 8) {
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// if we need to change the buffer size
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if (depth === 16) {
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outdata = Buffer.alloc(width * height * 4);
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}
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scaleDepth(indata, outdata, width, height, depth);
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}
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}
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return outdata;
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};
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