lockbits | 易学教程

Read and write directly to Unlocked Bitmap unmanaged memory (Scan0)

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问题 Is that ok to Write and Read directly from a unlocked Bitmap unmanaged memory? Can I keep using the BitmapData after I UnlockBits of the Bitmap? I did a test app where I can read the pixel of the Bitmap of a PictureBox at mouse position while another thread is writing pixels to the same Bitmap. EDIT 1: As Boing have pointed out in his answer: "Scan0 does not point to the actual pixel data of the Bitmap object; rather, it points to a temporary buffer that represents a portion of the pixel data

C# LockBits perfomance (int[,] to byte[])

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Graphics g; using (var bmp = new Bitmap(_frame, _height, PixelFormat.Format24bppRgb)) { var data = bmp.LockBits(new Rectangle(0, 0, _frame, _height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); var bmpWidth = data.Stride; var bytes = bmpWidth * _height; var rgb = new byte[bytes]; var ptr = data.Scan0; Marshal.Copy(ptr, rgb, 0, bytes); for (var i = 0; i < _frame; i++) { var i3 = (i << 1) + i; for (var j = 0; j < _height; j++) { var ij = j * bmpWidth + i3; var val = (byte)(_values[i, j]); rgb[ij] = val; rgb[ij + 1] = val; rgb[ij + 2] = val; } } Marshal.Copy(rgb, 0, ptr, bytes); bmp

Does Bitmap.LockBits “pin” a bitmap into memory?

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I'm using locked bitmaps a lot recently, and I keep getting "attempted to access invalid memory" errors. This is mostly because the bitmap has been moved in memory. Some people using GCHandle.Alloc() to allocate memory in the CLR and pin it. Does Bitmap.LockBits() do the same? I don't understand the difference between "locking" memory and "pinning" memory. Can you also explain the terminology and the differences if any? GCHandle.Alloc is a more generic method, that allows you to allocate a handle to any managed object and pin it in memory (or not). Pinning memory prevents GC from moving it

LockBits image rotation method not working?

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Hey all. I resorted to using LockBits for 2d bitmap image rotation after getting fed up with the slow performance and wacky behavior of both Get/Set Pixel, and RotateTransfom. So here is the code I've come up with, and by my reckoning, it should work perfectly. It doesn't. private static void InternalRotateImage(Bitmap originalBitmap, Bitmap rotatedBitmap, PointF centerPoint, float theta) { BitmapData originalData = originalBitmap.LockBits( new Rectangle(0, 0, originalBitmap.Width, originalBitmap.Height), ImageLockMode.ReadOnly, originalBitmap.PixelFormat); BitmapData rotatedData =

How can I color pixels that are not black in bitmap in yellow using LockBits?

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Using GetPixel and SetPixel is easy but very slow so I'm trying to using LockBits. I have this method I did long time ago to compare between two images: public static Bitmap FastComparison(Bitmap bmp1,Bitmap bmp2) { tolerancenumeric = 15; int tolerance = tolerancenumeric * tolerancenumeric + tolerancenumeric * tolerancenumeric + tolerancenumeric * tolerancenumeric; //dr * dr + dg * dg + db * db; bmp3 = new Bitmap(512,512); PixelFormat pxf = PixelFormat.Format24bppRgb; Rectangle rect = new Rectangle(0, 0, bmp1.Width, bmp1.Height); BitmapData bmpData1 = bmp1.LockBits(rect, ImageLockMode

LockBits image rotation method not working?

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问题 Hey all. I resorted to using LockBits for 2d bitmap image rotation after getting fed up with the slow performance and wacky behavior of both Get/Set Pixel, and RotateTransfom. So here is the code I've come up with, and by my reckoning, it should work perfectly. It doesn't. private static void InternalRotateImage(Bitmap originalBitmap, Bitmap rotatedBitmap, PointF centerPoint, float theta) { BitmapData originalData = originalBitmap.LockBits( new Rectangle(0, 0, originalBitmap.Width,

How can I color pixels that are not black in bitmap in yellow using LockBits?

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问题 Using GetPixel and SetPixel is easy but very slow so I'm trying to using LockBits. I have this method I did long time ago to compare between two images: public static Bitmap FastComparison(Bitmap bmp1,Bitmap bmp2) { tolerancenumeric = 15; int tolerance = tolerancenumeric * tolerancenumeric + tolerancenumeric * tolerancenumeric + tolerancenumeric * tolerancenumeric; //dr * dr + dg * dg + db * db; bmp3 = new Bitmap(512,512); PixelFormat pxf = PixelFormat.Format24bppRgb; Rectangle rect = new