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POHow to make ARGB transparency using bitwise operators
 

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  1. POHow to make ARGB transparency using bitwise operators
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    <p>I need to make transparency, having 2 pixels:</p> <p><code>pixel1: {A, R, G, B} - foreground pixel<br> pixel2: {A, R, G, B} - background pixel</code></p> <p>A,R,G,B are Byte values</p> <p>each color is represented by byte value</p> <p>now I'm calculating transparency as:</p> <p><code>newR = pixel2_R * alpha / 255 + pixel1_R * (255 - alpha) / 255<br> newG = pixel2_G * alpha / 255 + pixel1_G * (255 - alpha) / 255<br> newB = pixel2_B * alpha / 255 + pixel1_B * (255 - alpha) / 255</code></p> <p>but it is too slow I need to do it with bitwise operators (<strong>AND,OR,XOR, NEGATION, BIT MOVE</strong>)</p> <p>I want to do it on Windows Phone 7 XNA</p> <p>---attached C# code---</p> <pre><code> public static uint GetPixelForOpacity(uint reduceOpacityLevel, uint pixelBackground, uint pixelForeground, uint pixelCanvasAlpha) { byte surfaceR = (byte)((pixelForeground &amp; 0x00FF0000) &gt;&gt; 16); byte surfaceG = (byte)((pixelForeground &amp; 0x0000FF00) &gt;&gt; 8); byte surfaceB = (byte)((pixelForeground &amp; 0x000000FF)); byte sourceR = (byte)((pixelBackground &amp; 0x00FF0000) &gt;&gt; 16); byte sourceG = (byte)((pixelBackground &amp; 0x0000FF00) &gt;&gt; 8); byte sourceB = (byte)((pixelBackground &amp; 0x000000FF)); uint newR = sourceR * pixelCanvasAlpha / 256 + surfaceR * (255 - pixelCanvasAlpha) / 256; uint newG = sourceG * pixelCanvasAlpha / 256 + surfaceG * (255 - pixelCanvasAlpha) / 256; uint newB = sourceB * pixelCanvasAlpha / 256 + surfaceB * (255 - pixelCanvasAlpha) / 256; return (uint)255 &lt;&lt; 24 | newR &lt;&lt; 16 | newG &lt;&lt; 8 | newB; } </code></pre>
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