Thread: Creating Bitmap from byte[]

I cant seem to get this to work. I have a program in C++ that returns to my C# app through a DLL a char* (byte[]) on the C# side. The image data is stored as RGBA, I am trying to turn this into a bitmap, however when trying to create it from a stream i get an exception of:

Parameter is not valid.

I also tried:

Code:

Bitmap bmp = new Bitmap(width,height);

BitmapData bmpData = bmp.LockBits(new Rectangle(0,0,width,height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
Marshal.Copy(imgData, 0, bmpData.Scan0, imgData.Length);
bmp.UnlockBits(bmpData);

Which sort of works however all the image colors are now way off, and I know this is due to the PixelFormat, is there no way to do this without swapping pixels in the data?

[Edit]
Well I tried swapping all the bytes from RGBA to ARGB and that just made it look even worse.

That is basically what I tried, from what I understand you can only create the file from the stream if the stream has the bitmap header information in it.

Well I solved the problem. Even though the image was in RGBA format it was being displayed wrong, I swapped the R and B ad now the image shows up correctly, using the LockBits and UnlockBits method.

Originally Posted by xds4lx

Well I solved the problem. Even though the image was in RGBA format it was being displayed wrong, I swapped the R and B ad now the image shows up correctly, using the LockBits and UnlockBits method.

It's probably endian issues. 32bppARGB (which is what pixel format C# is expecting) is stored as a 32 bit number with alpha in the most-significant-byte, red in the second-most-significant-byte, etc.

Now, on a big-endian machine this would be the same as the order of the bytes within the 32-bit integer, but on a little-endian machine, blue is stored and read first (at the lowest byte address), then green, red, alpha. So if you're writing bytewise, you need to write B G R A in order to read it as 32bppARGB.