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

[Andreas Weber]

URL:
  <http://savannah.gnu.org/bugs/?36820>

                 Summary: imread doesn't consider opacity in
Magick::BilevelType, Patch included
                 Project: GNU Octave
            Submitted by: andy1978
            Submitted on: Di 10 Jul 2012 08:37:48 GMT
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: Andreas Weber
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: GNU/Linux

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Details:

$hg id
c3fd61c59e9c+ tip

I've attached an image "rect.png" of type Magick::BilevelType. When imread in
octave, the return value is empty(all zero):


    octave:1> pic=imread("rect.png");
    warning: your version of GraphicsMagick limits images to 16 bits per
pixel
    octave:2> min(pic(:))
    ans = 0
    octave:3> max(pic(:))
    ans = 0
    octave:4> imfinfo("rect.png")
    ans =
     
      scalar structure containing the fields:
     
        Filename =
/home/andy/Holografie/doc/Experimente/ShowHologramFromPNG/rect.png
        FileModDate = 26-Mar-2012 17:03:18
        FileSize =  9053
        Height =  600
        Width =  800
        BitDepth =  8
        Format = PNG
        LongFormat = Portable Network Graphics
        XResolution =  35.430
        YResolution =  35.430
        TotalColors =  1
        TileName =
        AnimationDelay = 0
        AnimationIterations = 0
        ByteOrder = undefined
        Gamma =  0.45455
        Matte =  1
        ModulusDepth =  8
        Quality =  75
        QuantizeColors =  256
        ResolutionUnits = undefined
        ColorType = grayscale
        View =


output of gm identify

   $gm identify rect.png
    rect.png PNG 800x600+0+0 DirectClass 8-bit 8.8K 0.000u 0:01


In __magick_read__.cc:220 there is a switch for BilevelType and GrayscaleType.
Afterwards, the red channel of PixelPacket is read but it looks to me taht
instead opacity should be used (red is always zero) when type==BilevelType.
The attached patch solves my problem but I'm not really sure about the side
effects.

Perhaps we can include some small sample images of various types and run some
tests against them?

Andy





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File Attachments:


-------------------------------------------------------
Date: Di 10 Jul 2012 08:37:48 GMT  Name: rect.png  Size: 9kB   By: andy1978

<http://savannah.gnu.org/bugs/download.php?file_id=26174>
-------------------------------------------------------
Date: Di 10 Jul 2012 08:37:48 GMT  Name: magick_read_BilevelType_opacity.patch
 Size: 904B   By: andy1978

<http://savannah.gnu.org/bugs/download.php?file_id=26175>

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  <http://savannah.gnu.org/bugs/?36820>

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