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    <p><code>Color</code> in java is defined in a packed integer,that is in a 32 bit integer the first 8 bits are alpha, next 8 are red, next 8 are green and last 8 are blue.</p> <p>Suppose the following is an 32 bit integer representing a color.Then,</p> <pre><code>AAAAAAAA RRRRRRRR GGGGGGGG BBBBBBBB ^Alpha ^Red ^Green ^Blue </code></pre> <p>That is, each of alpha, red, green and blue are basically 8 bits with values from 0 to 255 (the color range). So when you would want to combine these individual components back into the 32 bit integer color you should write</p> <p><code>color=alpha&lt;&lt;24 | red&lt;&lt;16 | green&lt;&lt;8 | blue</code></p> <p>So as per the rules change the code to the following</p> <pre><code>if(channel.equals(EIsolateChannel.ISOLATE_RED_CHANNEL)) { newPixel = newPixel | iRed&lt;&lt;16; //Can also write newPixel=iRed , since newPixel is always 0 before this } if(channel.equals(EIsolateChannel.ISOLATE_GREEN_CHANNEL)) { newPixel = newPixel | iGreen&lt;&lt;8; } if(channel.equals(EIsolateChannel.ISOLATE_BLUE_CHANNEL)) { newPixel = newPixel | iBlue; } </code></pre> <p><sup><strong>Note</strong> : I have ORed the <code>newPixel</code> before each component to allow display of multiple channels simultaneously, i.e you could display red and green with blue turned off.</sup></p> <hr> <p><strong>UPDATE</strong></p> <p>The second error you are getting is due to the fact that you are not resetting the value of <code>newPixel</code> after each iteration. So to fix it add the line <code>newPixel=0</code> within the loop. Your code should be</p> <pre><code>newPixel=0; //Add this line iAlpha=new Color(img.getRGB(x, y)).getAlpha(); iRed=new Color(img.getRGB(x, y)).getRed(); iGreen=new Color(img.getRGB(x, y)).getGreen(); iBlue=new Color(img.getRGB(x, y)).getBlue(); </code></pre> <hr> <p>For added efficiency I would suggest using <code>bitshifts</code> for obtaining the red, green, blue, and the alpha.</p> <pre><code>int rgb = img.getRGB(x,y); iAlpha = rgb&gt;&gt;24 &amp; 0xff; iRed = rgb &gt;&gt;16 &amp; 0xff; iGreen = rgb&gt;&gt;8 &amp; 0xff; iBlue = rgb &amp; 0xff; </code></pre> <p>This code would run faster as it does not creates 4 <code>Color</code> objects for each pixel in the source image</p>
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    1. COHmm, nice tutor and thank you very much, but now I load some image and when I apply a color filter, I get image filled with that color - image dissapears, I get colored rectangle (if I select red filter, I get red rectangle of image size, if I select green filter, I get green rectangle and same situation is with blue filter)
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    2. CO@MarkoFrelih See my updated answer.
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