b38dea0597
Share Gaia assets and adapters, keep private profiles and development documents local, and update both public READMEs.
104 lines
2.8 KiB
JavaScript
Executable file
104 lines
2.8 KiB
JavaScript
Executable file
/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
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// see http://www.wapforum.org/what/technical/SPEC-WAESpec-19990524.pdf
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/*exported WBMP */
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'use strict';
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var WBMP = (function(document) {
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function decode(arrayBuffer, callback) {
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// Pointer into the byte stream.
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var bytes = new Uint8Array(arrayBuffer);
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var ptr = 0;
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// Read unsigned octet from the byte stream.
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function readOctet() {
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return bytes[ptr++] & 0xff;
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}
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// Read unsigned multi-byte integer (6.3.1) from the byte stream.
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function readMultiByteInteger() {
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var result = 0;
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while (true) {
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if (result & 0xfe000000) {
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throw 'error parsing integer';
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}
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var b = bytes[ptr++];
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result = (result << 7) | (b & 0x7f);
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if (!(b & 0x80)) {
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return result;
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}
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}
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}
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// write a pixel
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function write(data, w, bit) {
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var color = bit ? 255 : 0;
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data[w] = color;
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data[w + 1] = color;
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data[w + 2] = color;
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data[w + 3] = 255;
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}
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try {
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// We only support image type 0: B/W, no compression
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if (readMultiByteInteger() !== 0) {
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return false;
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}
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// We don't expect any extended headers here.
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if (readOctet() !== 0) {
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return false;
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}
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var width = readMultiByteInteger();
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var height = readMultiByteInteger();
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// Reject incorrect image dimensions.
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if (width === 0 || width > 65535 || height === 0 || height > 65535) {
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return false;
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}
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// Create a canvas to draw the pixels into.
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var canvas = document.createElement('canvas');
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canvas.setAttribute('width', width);
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canvas.setAttribute('height', height);
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var ctx = canvas.getContext('2d', { willReadFrequently: true });
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var imageData = ctx.createImageData(width, height);
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var data = imageData.data;
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// Decode the image.
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for (var y = 0; y < height; ++y) {
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for (var x = 0; x < width; x += 8) {
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var bits = bytes[ptr++];
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var w = (y * width + x) * 4;
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write(data, w, bits & 0x80);
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write(data, w + 4, bits & 0x40);
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write(data, w + 8, bits & 0x20);
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write(data, w + 12, bits & 0x10);
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write(data, w + 16, bits & 0x08);
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write(data, w + 20, bits & 0x04);
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write(data, w + 24, bits & 0x02);
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write(data, w + 28, bits & 0x01);
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}
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}
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if (ptr > bytes.length) {
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return null;
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}
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// Update the canvas pixels.
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ctx.putImageData(imageData, 0, 0);
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// Convert to an image.
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canvas.toBlob(callback);
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} catch (e) {
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// Error occured.
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return null;
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}
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}
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return {
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decode: decode
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};
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})(document);
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