Add a bitmap header to a byte array then create a bitmap file

Question

I have a ByteArray from a camera，it's just a stream and has no bitmapheader.

I have searched for a demo,but they are all in C++.

I try to add a bitmapheader to my code, but a ParameterException is thrown. How do I make a bitmap file from the ByteArray?

Answer 1

You can't make a bitmap class directly with a raw data that doesn't have the bitmap header. The bitmap header is like a recipe for a bitmap image. It includes the essential information about width, height, bit per pixels, length of the data, and etc in order to make a proper array for the image.

Making the bitmap header is fairly easy if you take a close look at the bitmap header structure here

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But nothing is better than a complete example of a source code.

I broke them down into some pieces and commented on the each steps for you throughout the whole process. It probably looks a bit excessive and verbose, but it's going to be a good guide for you I guess.

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Following is an example of a 2×2 pixel, 24-bit bitmap (Windows DIB header BITMAPINFOHEADER) with pixel format RGB24.

BMP file format - Wikipedia

#region Bitmap Making...

// BmpBufferSize : a pure length of raw bitmap data without the header.
// the 54 value here is the length of bitmap header.
byte[] BitmapBytes = new byte[BmpBufferSize + 54];

#region Bitmap Header
// 0~2 "BM"
BitmapBytes[0] = 0x42;
BitmapBytes[1] = 0x4d;

// 2~6 Size of the BMP file - Bit cound + Header 54
Array.Copy(BitConverter.GetBytes(BmpBufferSize + 54), 0, BitmapBytes, 2, 4);

// 6~8 Application Specific : normally, set zero
Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 6, 2);

// 8~10 Application Specific : normally, set zero
Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 8, 2);

// 10~14 Offset where the pixel array can be found - 24bit bitmap data always starts at 54 offset.
Array.Copy(BitConverter.GetBytes(54), 0, BitmapBytes, 10, 4);
#endregion

#region DIB Header
// 14~18 Number of bytes in the DIB header. 40 bytes constant.
Array.Copy(BitConverter.GetBytes(40), 0, BitmapBytes, 14, 4);
                    
// 18~22 Width of the bitmap.
Array.Copy(BitConverter.GetBytes(image.Width), 0, BitmapBytes, 18, 4);

// 22~26 Height of the bitmap.
Array.Copy(BitConverter.GetBytes(image.Height), 0, BitmapBytes, 22, 4);

// 26~28 Number of color planes being used
Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 26, 2);

// 28~30 Number of bits. If you don't know the pixel format, trying to calculate it with the quality of the video/image source.
if (image.PixelFormat == System.Drawing.Imaging.PixelFormat.Format24bppRgb)
{                        
    Array.Copy(BitConverter.GetBytes(24), 0, BitmapBytes, 28, 2);
}

// 30~34 BI_RGB no pixel array compression used : most of the time, just set zero if it is raw data.
Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 30, 4);

// 34~38 Size of the raw bitmap data ( including padding )
Array.Copy(BitConverter.GetBytes(BmpBufferSize), 0, BitmapBytes, 34, 4);

// 38~46 Print resolution of the image, 72 DPI x 39.3701 inches per meter yields
if (image.PixelFormat == System.Drawing.Imaging.PixelFormat.Format24bppRgb)
{
    Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 38, 4);
    Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 42, 4);
}

// 46~50 Number of colors in the palette
Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 46, 4);

// 50~54 means all colors are important
Array.Copy(BitConverter.GetBytes(0), 0, BitmapBytes, 50, 4);

// 54~end : Pixel Data : Finally, time to combine your raw data, BmpBuffer in this code, with a bitmap header you've just created.
Array.Copy(BmpBuffer as Array, 0, BitmapBytes, 54, BmpBufferSize);

#endregion - bitmap header process
#endregion - bitmap making process