[Octave-bug-tracker] [bug #36820] imread doesn't consider opacity in Magick::BilevelType, Patch included

[Andreas Weber]

Follow-up Comment #2, bug #36820 (project octave):

This is the output of matlab:

>> [img,map,alpha]=imread('rect.png');
> size(img)
ans =   600   800     3

> size(map) 
ans =     0     0

> size(alpha) 
ans = 600   800

> mean(img(:))
ans = 0
 
mean(alpha(:)) 
ans = 5.66368125
 
> min(alpha(:))
ans = 0
 
> max(alpha(:))
ans = 255


 * In contrast to octave, matlab returns a 600x800x3 (RGB) matrix instead of a
600x800x1 graylevel

 * alpha channel is size 600x800 and corresponds to the image opacity but is
"inverted" to graphicsmagick: 0=transparent, 255=opaque. Therefore
mean(alpha)=255-249.34=5.66

btw, the original image was created with inkscape and then downscaled.


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