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POHow to get pixel data from canvas which contains the screenshot generated by a chrome extension?
 

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  1. POHow to get pixel data from canvas which contains the screenshot generated by a chrome extension?
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    <p>I am trying to implement a very simple color picker chrome extension. The idea is simple.</p> <ol> <li>make use of the captureVisibleTab API provided by chrome to get screenshot of current page at regular intervals.</li> <li>load this screenshot in a canvas and then use get getImageData method for canvas context and display color values of the pixel based on the mouse coordinates.</li> </ol> <p>I thought the idea was fairly simple to implement, but it actually did not turn out so well. Any help with the following snippets would be helpful:</p> <p>background.js (working perfectly!)</p> <pre><code>chrome.extension.onMessage.addListener(function(request, sender, sendResponse) { if (request.action == 'capture') { chrome.tabs.captureVisibleTab(null, null, function(dataUrl) { sendResponse({ imageUrl: dataUrl }); }); } return true; }); </code></pre> <p>content_script.js</p> <pre><code>function fill_canvas(){ chrome.extension.sendMessage({action: 'capture'}, function(response) { canvas = document.createElement('canvas'); canvas.width= $(window).width(); canvas.width= $(window).height(); canvasContext = canvas.getContext('2d'); var img = new Image(); img.onLoad = function(){ canvasContext.drawImage(img, 0, 0); } img.src = response.imageUrl; }); } $(document).ready(function(){ fill_canvas(); $(document).mousemove(function(e) { pixelData = canvasContext.getImageData(e.offsetX,e.offsetY, 1, 1).data; console.log(pixelData); }); }); </code></pre> <p><strong>Please expect the surrounding code to be working correctly (like the simple activate extension button) and all relevant permissions granted in the manifest.</strong></p> <p>The output generated for pixelData looks Like:</p> <pre><code>[0, 0, 0, 0, byteLength: 4, byteOffset: 0, buffer: ArrayBuffer, subarray: function, set: function…] </code></pre> <p>which on opening contains lot's of info, except the one I need.</p> <p>Cheers!</p>
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    1. USwhizzzkid
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      1. POHow to get pixel data from canvas which contains the screenshot generated by a chrome extension?
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    1. COYou state we should expect the surrounding code to work correctly, but I still need to ask if you have double-checked that response.imageUrl actually contain any data? (what does it contain if you console.log(response.imageUrl) it).
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      1. POHow to get pixel data from canvas which contains the screenshot generated by a chrome extension?
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    2. COhi @Ken-AbdiasSoftware it contains the dataurl, which opens as image in browser. It is a screenshot of current visible area in tab. please refer to this paste http://pastebin.com/HMTZdP2D and try opening the data url in your browser.
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      1. POHow to get pixel data from canvas which contains the screenshot generated by a chrome extension?
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