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POImage stride for MSpaint image in C# is +1 byte, why?
 

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  1. POImage stride for MSpaint image in C# is +1 byte, why?
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    <p>I have a problem regarding some pixel-based operations in C#. I wrote a class that serves as an image shell around a <a href="http://msdn.microsoft.com/en-us/library/4e7y164x.aspx" rel="nofollow">Bitmap</a>. It can give you the RGB values of a pixel at a certain (x,y) location in the image much faster than the <code>Bitmap.GetRGB(x,y)</code> color object by using <a href="http://msdn.microsoft.com/en-us/library/system.drawing.bitmap.aspx" rel="nofollow">BitmapData</a> and <a href="http://msdn.microsoft.com/en-us/library/system.drawing.bitmap.lockbits.aspx" rel="nofollow">LockBits</a> to get direct access to the image array and read the bytes from there. I added this function to get the RGB in an <code>0x00RRGGBB</code> mask at a (x,y) pixel.</p> <pre><code>public unsafe int getPixel(int x, int y) { byte* imgPointer = (byte*)bmpData.Scan0; int pixelPos = 0; if (y &gt; 0) pixelPos += (y * bmpData.Stride); pixelPos += x * (hasAlpha ? 4 : 3); int blue = *(imgPointer + pixelPos); int green = *(imgPointer + pixelPos + 1); int red = *(imgPointer + pixelPos + 2); int rgb = red &lt;&lt; 16; rgb += green &lt;&lt; 8; rgb += blue; return rgb; } </code></pre> <p>This works flawlessly for all the images I've worked with thus far, except for any image I generate using MSPaint. For example, I made a 5x1 image in paint containing 5 shades of yellow. When I load this image into my program however, the image stride is 16! I suspected it to be 15 (3 bytes per pixel, 5 pixels) but for some reason after the first three bytes (first pixel) there is an extra byte, and then the rest of the pixels follow in the array.</p> <p>I have only found this for images that are saved by MSpaint and I was hoping anyone could explain me what that extra byte is for and how to detect that extra byte.</p>
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