1993.08.23 04:08 "Re: help on TIFFReadRGBAImage", by Yip Chi Lap

Hi,

For what it's worth, the PPM standard specifies that the first pixel in the file is in the lower left corner. This is always the case, and it can't be set to anything else from within the PPM file.

Shouldn't it be top-left corner? The ppm(5) manpage reads:

......

- Width * height pixels, each three ASCII decimal values between 0 and the specified maximum value, starting at the top-left corner of the pixmap, proceeding in normal English reading order. The three values for each pixel represent red, green, and blue, respectively; a value of 0 means that color is off, and the maximum value means that color is maxxed out.

......

By the way, the "(row,col)" in my mail about what (x,y) means some time ago:

> So the "(x,y)" in the sentence "Note that the raster is assume to
> be organized such that the pixel at location (x,y) is raster[y*width+x]"
> in the man page of TIFFReadRGBAImage refers to the 'normal' cartesian
> coordinates but not the (row,col) coordinate relative to the image, I
> suppose?

should read "(col,row)". Thanks all who helped. :)

Regards,
  Beta.

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