2003.03.18 22:58 "Grayscale 16-bit images", by Claus Ekstroem

Hi,

I'm completely new to tiff images and libtiff in particular so bear with me if I asking something that is beeding obvious. From searching the net (and the archives) I can see that this seems to be a fairly common answer, but I can't find any solutions or real documentation to guide me. So here goes....

I'm trying to read a 16-bit grayscale image:

Width           2200
Height          1695
BitsPerSample   16
SamplesPerPixel 1

The pixels are a scan from a microarray experiment (a "DNA chip") sp I need to access the intensities of each pixel and I need all 16 bits of information. Currently, I considered the following piece of code:

     if (TIFFReadRGBAImage(tif, imageWidth, imageHeight, raster, 0)) {
          long index = 0;
          for (e = imageHeight-1; e!=-1; e--) {
            for(c = 0; c < imageWidth; c++){
              int Red = TIFFGetR(raster[e * imageWidth + c]);
              int Green = TIFFGetG(raster[e * imageWidth + c]);
              int Blue = TIFFGetB(raster[e * imageWidth + c]);
              data[index] = Red;
              index++;
            }

          }
      }

but that is clealy wrong as the image is converted to 8 bit and the colour-channels become identical. I figure reading the file as a RGBAImage is the wrong approach, so could someone mail me a couple of lines of code to read and access the individual pixels?

All the best,

Claus

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Claus Thorn Ekstrøm <ekstrom@dina.kvl.dk>
Dept of Mathematics and Physics, KVL
Thorvaldsensvej 40
DK-1871 Frederiksberg C
Denmark
Phone:[+45] 3528 2341
Fax: [+45] 3528 2350
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