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1999.07.15 23:47 "RGB Gradient Code, adapted from Andreas Neumann", by Eric B. Middlecamp
1999.07.16 06:23 "Re: RGB Gradient Code, adapted from Andreas Neumann", by Niles Ritter
1999.07.16 16:08 "Re: RGB Gradient Code, adapted from Andreas Neumann", by Eric B. Middlecamp
1999.07.16 16:17 "Re: RGB Gradient Code, adapted from Andreas Neumann", by Daniel McCoy
1999.07.16 17:39 "Re: RGB Gradient Code, adapted from Andreas Neumann", by Eric B. Middlecamp
1999.07.16 20:04 "Re: RGB Gradient Code, adapted from Andreas Neumann", by Phillip Crews

1999.07.15 23:47 "RGB Gradient Code, adapted from Andreas Neumann", by Eric B. Middlecamp

I made a simple extension to Andreas Neumann's gradient code, (see http://www.gis.univie.ac.at/strv/strv/leute/andi/computer/graphics/raster-formats/example_tiff_main.html) but the output TIFF image has some odd contamination. Looking at the image, you wouldn't be able to tell -- however a histogram reveals that some levels are omitted and others are doubled.

Has anyone else experienced bizarre anomalies like this?

Thanks,

Eric Middlecamp

// ======================================================

#include "tiffio.h"

void RGBGradient( char *tiff_fname )
{
     unsigned char color_ptr[256*3];
     int i, j;

     TIFF* tif = TIFFOpen(tiff_fname, "w");
     if (tif == NULL) {
          return;
     }

     TIFFSetField(tif, TIFFTAG_IMAGEWIDTH,         256);
     TIFFSetField(tif, TIFFTAG_IMAGELENGTH,        256);
     TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE,      8);
     TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL,    3);
     TIFFSetField(tif, TIFFTAG_PHOTOMETRIC,        PHOTOMETRIC_RGB);

     TIFFSetField(tif, TIFFTAG_PLANARCONFIG,            PLANARCONFIG_CONTIG);
     TIFFSetField(tif, TIFFTAG_ROWSPERSTRIP,  1);

     for (i = 0; i < 256; i++) {

          for (j = 0; j < 256; j++) {
               color_ptr[j*3+0] = i;
               color_ptr[j*3+1] = i;
               color_ptr[j*3+2] = i;

          }
          TIFFWriteScanline(tif, color_ptr, i);
     }

     TIFFFlushData(tif);
     TIFFClose(tif);
}

// ======================================================