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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
This commit is contained in:
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/fish.jpg Normal file
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examples/image_decoders/jpeg_viewer.html Normal file
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<!DOCTYPE html>
<!--
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.
-->
<html dir="ltr" mozdisallowselectionprint>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<meta name="google" content="notranslate">
<title>PDF.js standalone JpegImage parser</title>
<style>
body {
background-color: #808080;
margin: 0;
padding: 0;
}
</style>
<script src="../../node_modules/pdfjs-dist/image_decoders/pdf.image_decoders.js"></script>
</head>
<body tabindex="1">
<canvas id="jpegCanvas" width="0" height="0"></canvas>
<script src="jpeg_viewer.js"></script>
</body>
</html>

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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);