98 lines
3.1 KiB
JavaScript
98 lines
3.1 KiB
JavaScript
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class CThumbnailLoader {
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constructor() {
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this.binaryFormat = null;
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this.data = null;
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this.width = 0;
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this.heightOne = 0;
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}
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load(url, callback) {
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if (!callback)
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return;
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let xhr = new XMLHttpRequest();
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xhr.open('GET', url + ".bin", true);
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xhr.responseType = 'arraybuffer';
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if (xhr.overrideMimeType)
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xhr.overrideMimeType('text/plain; charset=x-user-defined');
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else xhr.setRequestHeader('Accept-Charset', 'x-user-defined');
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xhr.onload = e => {
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// TODO: check errors
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this.binaryFormat = e.target.response;
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callback();
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};
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xhr.send(null);
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}
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_openBinary(arrayBuffer) {
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//var t1 = performance.now();
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const binaryAlpha = new Uint8Array(arrayBuffer);
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this.width = (binaryAlpha[0] << 24) | (binaryAlpha[1] << 16) | (binaryAlpha[2] << 8) | (binaryAlpha[3] << 0);
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this.heightOne = (binaryAlpha[4] << 24) | (binaryAlpha[5] << 16) | (binaryAlpha[6] << 8) | (binaryAlpha[7] << 0);
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const count = (binaryAlpha[8] << 24) | (binaryAlpha[9] << 16) | (binaryAlpha[10] << 8) | (binaryAlpha[11] << 0);
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const height = count * this.heightOne;
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this.data = new Uint8ClampedArray(4 * this.width * height);
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var binaryIndex = 12;
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var imagePixels = this.data;
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var index = 0;
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var len0 = 0;
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var tmpValue = 0;
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while (binaryIndex < binaryAlpha.length) {
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tmpValue = binaryAlpha[binaryIndex++];
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if (0 == tmpValue) {
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len0 = binaryAlpha[binaryIndex++];
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while (len0 > 0) {
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len0--;
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imagePixels[index] = imagePixels[index + 1] = imagePixels[index + 2] = 255;
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imagePixels[index + 3] = 0; // this value is already 0.
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index += 4;
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}
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} else {
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imagePixels[index] = imagePixels[index + 1] = imagePixels[index + 2] = 255 - tmpValue;
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imagePixels[index + 3] = tmpValue;
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index += 4;
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}
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}
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//var t2 = performance.now();
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//console.log(t2 - t1);
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};
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getImage = function(index, canvas, ctx) {
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//var t1 = performance.now();
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if (!canvas) {
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canvas = document.createElement("canvas");
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canvas.width = this.width;
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canvas.height = this.heightOne;
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canvas.style.width = iconWidth + "px";
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canvas.style.height = iconHeight + "px";
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ctx = canvas.getContext("2d");
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}
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if (!this.data) {
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this._openBinary(this.binaryFormat);
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delete this.binaryFormat;
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}
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let dataTmp = ctx.createImageData(this.width, this.heightOne);
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const sizeImage = 4 * this.width * this.heightOne;
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dataTmp.data.set(new Uint8ClampedArray(this.data.buffer, index * sizeImage, sizeImage));
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ctx.putImageData(dataTmp, 0, 0);
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//var t2 = performance.now();
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//console.log(t2 - t1);
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return canvas;
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};
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};
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export default CThumbnailLoader; |