C# – Getting color image from bitmap while image is 16bppGrayscale

bitmapcimaging

Problem No1.
My own Related problem

I asked the next question here

Now the Problem No 2 is.

When i am trying to open 16 Bit (Monocrome ) images from their raw pixel data
then i am getting Error.
Because i am using PixelFormat.Format16bppGrayscale on creation of Bitmap like

Bitmap bmp = new Bitmap(Img_Width, Img_Height,PixelFormat.Format16bppGrayscale);

So googled and found Format16bppGrayscale not supported so i modifed my code like below.

 PixelFormat format = PixelFormat.Format16bppRgb565;
 Bitmap bmp = new Bitmap(Img_Width, Img_Height, format);
 Rectangle rect = new Rectangle(0, 0, Img_Width, Img_Height);
 BitmapData bmpData = bmp.LockBits(rect, ImageLockMode.ReadWrite, format);
 Marshal.Copy(rawPixel, 0, bmpData.Scan0, rawPixel.Length);
 bmp.UnlockBits(bmpData);

Amazing thing is that i am getting the image now because i change the pixelFormat.
But problem is that My monocrome (Grayscale) image look in various color.

How can i get the original appearance. I tried several grayscale method but not successful
Please give me some unsafe code.
Thanks,

Best Answer

BobPowell's GDI+ FAQ has a bit about greyscale. The 16 bpp in .NET just doesn't work. I have to do everything in 32 bpp and resort to external tools for conversion. Luckily (?) I get to stick with TIFF images most of the time. Also, this thread might help.

Related Solutions

Android – Strange OutOfMemory issue while loading an image to a Bitmap object

To fix the OutOfMemory error, you should do something like this:

BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 8;
Bitmap preview_bitmap = BitmapFactory.decodeStream(is, null, options);

This inSampleSize option reduces memory consumption.

Here's a complete method. First it reads image size without decoding the content itself. Then it finds the best inSampleSize value, it should be a power of 2, and finally the image is decoded.

// Decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f) {
    try {
        // Decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(new FileInputStream(f), null, o);

        // The new size we want to scale to
        final int REQUIRED_SIZE=70;

        // Find the correct scale value. It should be the power of 2.
        int scale = 1;
        while(o.outWidth / scale / 2 >= REQUIRED_SIZE && 
              o.outHeight / scale / 2 >= REQUIRED_SIZE) {
            scale *= 2;
        }

        // Decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
    } catch (FileNotFoundException e) {}
    return null;
}

Android – Save bitmap to location

try (FileOutputStream out = new FileOutputStream(filename)) {
    bmp.compress(Bitmap.CompressFormat.PNG, 100, out); // bmp is your Bitmap instance
    // PNG is a lossless format, the compression factor (100) is ignored
} catch (IOException e) {
    e.printStackTrace();
}

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