161 lines
3.9 KiB
JavaScript
161 lines
3.9 KiB
JavaScript
"use strict";
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var PNG = function(){
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// initialize all members to keep the same hidden class
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this.width = 0;
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this.height = 0;
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this.bitDepth = 0;
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this.colorType = 0;
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this.compressionMethod = 0;
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this.filterMethod = 0;
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this.interlaceMethod = 0;
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this.colors = 0;
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this.alpha = false;
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this.pixelBits = 0;
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this.palette = null;
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this.pixels = null;
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};
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PNG.prototype.getWidth = function(){
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return this.width;
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};
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PNG.prototype.setWidth = function(width){
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this.width = width;
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};
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PNG.prototype.getHeight = function(){
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return this.height;
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};
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PNG.prototype.setHeight = function(height){
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this.height = height;
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};
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PNG.prototype.getBitDepth = function(){
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return this.bitDepth;
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};
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PNG.prototype.setBitDepth = function(bitDepth){
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if ([2, 4, 8, 16].indexOf(bitDepth) === -1){
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throw new Error("invalid bith depth " + bitDepth);
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}
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this.bitDepth = bitDepth;
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};
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PNG.prototype.getColorType = function(){
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return this.colorType;
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};
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PNG.prototype.setColorType = function(colorType){
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// Color Allowed Interpretation
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// Type Bit Depths
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//
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// 0 1,2,4,8,16 Each pixel is a grayscale sample.
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//
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// 2 8,16 Each pixel is an R,G,B triple.
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//
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// 3 1,2,4,8 Each pixel is a palette index;
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// a PLTE chunk must appear.
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//
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// 4 8,16 Each pixel is a grayscale sample,
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// followed by an alpha sample.
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//
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// 6 8,16 Each pixel is an R,G,B triple,
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// followed by an alpha sample.
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var colors = 0, alpha = false;
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switch (colorType){
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case 0: colors = 1; break;
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case 2: colors = 3; break;
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case 3: colors = 1; break;
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case 4: colors = 2; alpha = true; break;
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case 6: colors = 4; alpha = true; break;
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default: throw new Error("invalid color type");
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}
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this.colors = colors;
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this.alpha = alpha;
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this.colorType = colorType;
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};
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PNG.prototype.getCompressionMethod = function(){
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return this.compressionMethod;
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};
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PNG.prototype.setCompressionMethod = function(compressionMethod){
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if (compressionMethod !== 0){
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throw new Error("invalid compression method " + compressionMethod);
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}
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this.compressionMethod = compressionMethod;
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};
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PNG.prototype.getFilterMethod = function(){
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return this.filterMethod;
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};
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PNG.prototype.setFilterMethod = function(filterMethod){
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if (filterMethod !== 0){
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throw new Error("invalid filter method " + filterMethod);
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}
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this.filterMethod = filterMethod;
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};
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PNG.prototype.getInterlaceMethod = function(){
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return this.interlaceMethod;
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};
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PNG.prototype.setInterlaceMethod = function(interlaceMethod){
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if (interlaceMethod !== 0 && interlaceMethod !== 1){
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throw new Error("invalid interlace method " + interlaceMethod);
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}
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this.interlaceMethod = interlaceMethod;
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};
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PNG.prototype.setPalette = function(palette){
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if (palette.length % 3 !== 0){
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throw new Error("incorrect PLTE chunk length");
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}
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if (palette.length > (Math.pow(2, this.bitDepth) * 3)){
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throw new Error("palette has more colors than 2^bitdepth");
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}
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this.palette = palette;
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};
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PNG.prototype.getPalette = function(){
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return this.palette;
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};
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/**
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* get the pixel color on a certain location in a normalized way
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* result is an array: [red, green, blue, alpha]
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*/
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PNG.prototype.getPixel = function(x, y){
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if (!this.pixels) throw new Error("pixel data is empty");
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if (x >= this.width || y >= this.height){
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throw new Error("x,y position out of bound");
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}
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var i = this.colors * this.bitDepth / 8 * (y * this.width + x);
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var pixels = this.pixels;
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switch (this.colorType){
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case 0: return [pixels[i], pixels[i], pixels[i], 255];
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case 2: return [pixels[i], pixels[i + 1], pixels[i + 2], 255];
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case 3: return [
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this.palette[pixels[i] * 3 + 0],
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this.palette[pixels[i] * 3 + 1],
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this.palette[pixels[i] * 3 + 2],
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255];
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case 4: return [pixels[i], pixels[i], pixels[i], pixels[i + 1]];
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case 6: return [pixels[i], pixels[i + 1], pixels[i + 2], pixels[i + 3]];
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}
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};
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module.exports = PNG;
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