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Add a basic JpegImage example using the standalone image decoders

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The image was "borrowed" from one of the examples found at https://github.com/notmasteryet/jpgjs/tree/master/images
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Jonas Jenwald 2018-05-16 13:49:33 +02:00
parent 303537bcb1
commit 5984c24415
3 changed files with 115 additions and 0 deletions
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examples/image_decoders/jpeg_viewer.js Normal file
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/* Copyright 2018 Mozilla Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
if (!pdfjsImageDecoders.JpegImage) {
alert('Please build the pdfjs-dist library using `gulp dist-install`');
}
var JPEG_IMAGE = 'fish.jpg';
var jpegCanvas = document.getElementById('jpegCanvas');
var jpegCtx = jpegCanvas.getContext('2d');
// Load the image data, and convert it to a Uint8Array.
//
var nonBinaryRequest = false;
var request = new XMLHttpRequest();
request.open('GET', JPEG_IMAGE, false);
try {
request.responseType = 'arraybuffer';
nonBinaryRequest = request.responseType !== 'arraybuffer';
} catch (e) {
nonBinaryRequest = true;
}
if (nonBinaryRequest && request.overrideMimeType) {
request.overrideMimeType('text/plain; charset=x-user-defined');
}
request.send(null);
var typedArrayImage;
if (nonBinaryRequest) {
var str = request.responseText, length = str.length;
var bytes = new Uint8Array(length);
for (var i = 0; i < length; ++i) {
bytes[i] = str.charCodeAt(i) & 0xFF;
}
typedArrayImage = bytes;
} else {
typedArrayImage = new Uint8Array(request.response);
}
// Parse the image data using `JpegImage`.
//
var jpegImage = new pdfjsImageDecoders.JpegImage();
jpegImage.parse(typedArrayImage);
var width = jpegImage.width, height = jpegImage.height;
var jpegData = jpegImage.getData(width, height, /* forceRGB = */ true);
// Render the JPEG image on a <canvas>.
//
var imageData = jpegCtx.createImageData(width, height);
var imageBytes = imageData.data;
for (var i = 0, j = 0, ii = width * height * 4; i < ii;) {
imageBytes[i++] = jpegData[j++];
imageBytes[i++] = jpegData[j++];
imageBytes[i++] = jpegData[j++];
imageBytes[i++] = 255;
}
jpegCanvas.width = width, jpegCanvas.height = height;
jpegCtx.putImageData(imageData, 0, 0);