Loading 12 bit grayscale images

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#1 Posted : Tuesday, October 31, 2017 1:38:08 PM(UTC)

tbecker82

Groups: Registered
Posts: 37

Hi,

I have a question about how to handle 12 bit grayscale images.

We use a proprietary image format so I handle all of the image loading.
The raw data we get is a 16 bit image with the high bit set to 11 and the image
data ranging from 0 to 4095. How would I go about creating a RasterImage
from this?

This is how I currently load our 16 bit images.

RaasterImage img = RasterImage.CreateGrayscale(m_width, m_height, m_bpp, m_dpi); // m_bpp is 16

I then load the data manually using SetRow()

for (int count = 0; count < m_height; count++)
{
img.SetRow(count, m_imageData, count * m_width * (m_bpp / 8),
m_imageSize / m_height);
}

How does LeadTools store 12 bit data internally? I was assuming I still needed 2 bytes per pixel value
so I would have a 16 bit image with 12 bit values but that setup has caused problems with some of the filters.

Thank you

Tony


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#2 Posted : Friday, November 3, 2017 1:44:50 PM(UTC)

Anthony Northrup

Groups: Registered, Tech Support, Administrators
Posts: 199

Was thanked: 28 time(s) in 28 post(s)

Hello Tony,

After a some searching, I was able to find this old forum post about 12-bit grayscale images: https://www.leadtools.com/support/forum/posts/t4697-12-bit-Grayscale-images. Below are some helper functions I made to convert between a row of shorts (though you can change the type to int) to the byte array the SetRow function is expecting.

Code:


private byte[] CreatePair(short p1, short p2)
{
    // p1 = 0xABC
    // p2 = 0xDEF
    // res = [ BC, FA, DE ]
    return new byte[] { (byte)(p1 & 0xFF), (byte)(((p2 & 0xF) << 4) | ((p1 >> 8) & 0xF)), (byte)((p2 >> 4) & 0xFF) };
}
private byte[] CreateRow(short[] row)
{
    List<byte> res = new List<byte>();
    
    for (int i = 0; i < row.Length; i += 2)
    {
        byte[] pair;
        if (i + 1 < row.Length)
            pair = CreatePair(row[i], row[i + 1]);
        else // Handle odd length row, use 0x000 for next pixel
            pair = CreatePair(row[i], 0x000);
        
        res.AddRange(pair);
    }
    
    return res.ToArray();
}

And here’s a sample of how to use it:

Code:


private void Form1_Load(object sender, EventArgs e)
{
    int bpp = 12;
    int width = 5;
    int height = 2;
    int dpi = 1;
    
    RasterImage image = RasterImage.CreateGrayscale(width, height, bpp, dpi);
    
    // Gradient from black to white
    short[] row = new short[] { 0x000, 0x444, 0x888, 0xCCC, 0xFFF };
    byte[] row12 = CreateRow(row);
    image.SetRow(0, row12, 0, row12.Length);
}

Attached is the image this produces (see Screenshot_1.png).

File Attachment(s):

CAS-62070-G5Z8T7.zip (2kb) downloaded 537 time(s).

Edited by moderator Tuesday, November 7, 2017 4:00:51 PM(UTC) | Reason: Not specified

Anthony Northrup
Developer Support Engineer
LEAD Technologies, Inc.

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