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POErase parts of image to make pixels transparent
 

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    <p>I'm working in <em>openFrameworks</em>, a set of C++ libraries.</p> <p>What I'm trying to do is simply 'erase' certain pixels of an ofImage (a class that loads/displays an image, and has access to it's pixel array) when a shape (an eraser) passes over the appropriate pixels of the image. Pretty simple stuff - I think - but I'm having a mental block!</p> <p>ofImage has two methods - <code>getPixels()</code> and <code>getPixelsRef()</code> that seem to approach what I am trying to do, but the methodology I am using is not quite giving me the results I want.</p> <p>Here is an example of an attempt to update the pixels of a foreground image from the pixels of a background image:</p> <pre><code>ofPixelsRef fore = foreground.getPixelsRef(); ofPixelsRef back = background.getPixelsRef(); for(int x = 0; x &lt; foreground.getWidth()/2; x++) { for (int y = 0; y &lt; foreground.getHeight(); y++) { ofColor c = back.getColor(x, y); fore.setColor(x, y, c); } } </code></pre> <p>foreground.setFromPixels(fore);</p> <p>and here is an attempt to statically colour the foreground with a predetermined colour (which I think is what I want to do, with a transparent white ?!?):</p> <pre><code>ofPixelsRef fore = foreground.getPixelsRef(); ofColor c(0, 127); for(int x = 0; x &lt; foreground.getWidth(); x++) { for (int y = 0; y &lt; foreground.getHeight(); y++) { fore.setColor(x, y, c); } } foreground.setFromPixels(fore); </code></pre> <p>Neither are quite where I want to get to, but I think they're a stab in the right direction. If anyone has any ideas on where to proceed, I'm all ears. </p> <p>I'd consider moving to the ofFbo class, or even GLSL if there's a clean lead/example. Feel free to post vanilla C++ as well, and I'll see what I can do about porting it to oF.</p> <p>Thanks, </p> <p>~ Jesse</p>
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