C# - Can I use Libtiff to output Tiff encoded JPEG (In YCbCr)

StackOverflow https://stackoverflow.com/questions/19219651

  •  30-06-2022
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Question

Hi I am quite new to Libtiff and image processing, and I have a question when I try to use Libtiff.net from Bitmiracle.

I have some OJPEG TIFF image and want to convert them into nowadays JPEG TIFF. I achieved that by converting the source into BMP and then save as TIFF (compression: JPEG; photometric: RGB), but the size of the image is quite large. So I thought if I can compress them with photometric of YCbCr, which can reduce the size a lot.

However, when I change the photometric from RGB to YCbCr, the program just don't work: the output is only 8 bytes (the input is about 400kb). When open the image as TXT, it shows:

"II* "

The code I use is:

byte[] raster1 = getImageRasterBytes(inputbmp[0], PixelFormat.Format24bppRgb);
tif1.SetField(TiffTag.IMAGEWIDTH, inputbmp[0].Width);
tif1.SetField(TiffTag.IMAGELENGTH, inputbmp[0].Height);
tif1.SetField(TiffTag.COMPRESSION, Compression.JPEG);
tif1.SetField(TiffTag.PHOTOMETRIC, Photometric.YCBCR);
tif1.SetField(TiffTag.ROWSPERSTRIP, inputbmp[0].Height);
//tif1.SetField(TiffTag.JPEGQUALITY, confidence);
tif1.SetField(TiffTag.XRESOLUTION, 200);
tif1.SetField(TiffTag.YRESOLUTION, 200);
tif1.SetField(TiffTag.BITSPERSAMPLE,8);
tif1.SetField(TiffTag.SAMPLESPERPIXEL, 3);
int stride = raster1.Length / inputbmp[0].Height;
convertSamples(raster1, inputbmp[0].Width, inputbmp[0].Height);
for (int i = 0, offset = 0; i < inputbmp[0].Height; i++)
{
    tif1.WriteScanline(raster1, offset, i, 0);
    offset += stride;
}

I'm not quite sure if WriteScanline can handle YCbCr output or not, and if there are other ways, It's totally cool too.

Thank you for the help!

Was it helpful?

Solution

Output images are definetely broken. It usually happens when some fatal error occurred. The library should output warnings and errors into console in such a case.

Please investigate the warnings and errors. They might give you the answer.

Based on experience, I think you might have provided incorrect value for ROWSPERSTRIP tag. The value should be a multiple of 8.

OTHER TIPS

JPEG converts image into YCbCr internally already, so I don't think you will benefit from this.

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