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POUsing Bitmap.LockBits and Marshal.Copy in IronPython not changing image as expected
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  1. POUsing Bitmap.LockBits and Marshal.Copy in IronPython not changing image as expected
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    copied!<p>I have written the following IronPython code:</p> <pre><code>import clr clr.AddReference("System.Drawing") from System import * from System.Drawing import * from System.Drawing.Imaging import * def NoWorko(bitmap): bmData = bitmap.LockBits(Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb) total_bytes = (bmData.Stride) * bmData.Height rgbValues = Array.CreateInstance(Byte, total_bytes) Runtime.InteropServices.Marshal.Copy(bmData.Scan0, rgbValues, 0, total_bytes) for i in rgbValues: i = 255 - i #The following line doesn't appear to actually copy the bits back Runtime.InteropServices.Marshal.Copy(rgbValues, 0, bmData.Scan0, total_bytes) bitmap.UnlockBits(bmData) originalImage = Bitmap("Test.bmp") newPic = NoWorko(originalImage) newPic.Save("New.bmp") </code></pre> <p>Which is my interpretation of this MSDN code sample: <a href="http://msdn.microsoft.com/en-us/library/5ey6h79d.aspx" rel="nofollow noreferrer">http://msdn.microsoft.com/en-us/library/5ey6h79d.aspx</a> except that I am saving the altered bitmap instead of displaying it in a Form.</p> <p>The code runs, however the newly saved bitmap is an exact copy of the original image with no sign of any changes having occurred <strike><strong>(it's supposed to create a red tint)</strong></strike>. Could anyone advise what's wrong with my code?</p> <p><strike><strong>The image I'm using is simply a 24bpp bitmap I created in Paint (it's just a big white rectangle!)</strong></strike>, using IronPython 2.6 and on Windows 7 (x64) with .Net Framework 3.5 SP1 installed.</p> <p><strong>Update</strong></p> <p>My foolishness has been pointed out in trying to add a red tint to a white image - so now the code simply inverts the colours. I've tried this on a number of images, but it just doesn't seem to have any effect.</p> <p>However, the following (very similar) C# program:</p> <pre><code>public static void Main(string[] args) { Bitmap bitmap = new Bitmap("nTest.jpg"); BitmapData bmData = bitmap.LockBits( new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int total_bytes = (bmData.Stride) * bmData.Height; byte[] rgbValues = new byte[total_bytes]; Marshal.Copy(bmData.Scan0, rgbValues, 0, total_bytes); for(int i = 0; i &lt; total_bytes; i++) { rgbValues[i] = (byte)(255 - rgbValues[i]); } Marshal.Copy(rgbValues, 0, bmData.Scan0, total_bytes); bitmap.UnlockBits(bmData); bitmap.Save("nNew.jpg"); } </code></pre> <p>Worked on all the images I've tried.</p> <p>I'm not sure, but it seems to be something to do with the call to:</p> <p>Runtime.InteropServices.Marshal.Copy(rgbValues, 0, bmData.Scan0, bytes)</p> <p>in IPY that is causing the problem. </p>
 

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