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April 2008

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2008.04.23 13:58 "transparent tiff", by Roman Kazmin

Hi everybody. I'm trying to create transparent tiff file. But I receive 
usual tiff file. Where is my mistake? I'm trying to make following - red 
screen with transparent green rectange at the center. Below is my code:

int main(int argc, char **argv)
{
	 TIFF *tif;
	 char    buffer[4*1024];
	 int     width = 1024, height = 768, row;
	 uint32 temp = EXTRASAMPLE_ASSOCALPHA;
	 tif = TIFFOpen("3d.tif", "w");

	 TIFFSetField (tif, TIFFTAG_IMAGEWIDTH, width);
	 TIFFSetField (tif, TIFFTAG_IMAGELENGTH, height);
	 TIFFSetField (tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
	 TIFFSetField (tif, TIFFTAG_SAMPLESPERPIXEL,  4);
	 TIFFSetField (tif, TIFFTAG_BITSPERSAMPLE,    8);
	 TIFFSetField (tif, TIFFTAG_EXTRASAMPLES,     1, &temp);
	 TIFFSetField (tif, TIFFTAG_ORIENTATION, 
ORIENTATION_TOPLEFT);
	 TIFFSetField (tif, TIFFTAG_PHOTOMETRIC,      PHOTOMETRIC_RGB);
	 TIFFSetField (tif, TIFFTAG_IMAGEDESCRIPTION, "3D Simulation");
	 TIFFSetField (tif, TIFFTAG_COMPRESSION, 
COMPRESSION_PACKBITS);
	 TIFFSetField (tif, TIFFTAG_ROWSPERSTRIP,     16);

	 for (row = 0; row < 768; row++)
	 {
		 for (int i = 0; i < 1024; i++)
		 {
			 if(row > 234 && row < 530 && i > 350 && i < 
700)
			 {   // Here I'm trying to draw transparent 
green rectangle
				 buffer[4*i]   = 0;
				 buffer[4*i+1] = 200;
				 buffer[4*i+2] = 0;
				 buffer[4*i+3] = 200; // transparency
			 }
			 else
			 {
				 buffer[4*i]   = 200;
				 buffer[4*i+1] = 0;
				 buffer[4*i+2] = 0;
				 buffer[4*i+3] = 0;
			 }
		 }
		 TIFFWriteScanline(tif, buffer, row, 0);
	 }
	 TIFFClose(tif); tif = NULL;
	 return 0;
}