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

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!

Answer 1

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.

Answer 2

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