imagemagick6 import issue

[Sean Enck]

On 2018-11-03, Steve Allewell wrote:
> On 02/11/2018 23:51, Sean Enck wrote:
> > I was using kxstitch compiled against imagemagick V6 and it appears that 
> > image import doesn't work properly (running against the git head as 
> > we've already fixed the last issue). In V6 of imagemagick the import 
> > produces a completely black image. I bisected and was able to get to 
> > 295773f44bfda1227d85edf065a8de14dc889159 as the commit that caused the 
> > actual regression. The gist below is a partial revert where I was able 
> > to successfully import an image with colors (aka not all black).
> > 
> > Again this only against imagemagick V6.
> > 
> > Patch: https://gist.github.com/enckse/de74000c2fc41c3ceb90c97fa9693250
> > 
> > --Sean
> > 
> Hi Sean
> 
> Thanks for that.
> 
> The number of problems I have had keeping up with the changes in the Magick++ API, I have started looking at my own colour
> reduction/mapping code to try and get away from using it.
> 
> I'm not sure why the pixelColor function doesn't work in V6.  It is available in the API and it should return the same value as in V7.
> 
> The pixelColor code essentially does the same as your patch assuming the image is a DirectClass.
> The PseudoClass is for indexed colour palettes.
> -----------------------------
> Magick::Color Magick::Image::pixelColor(const ssize_t x_, const ssize_t y_) const
> {
>   ClassType
>     storage_class;
> 
>   storage_class=classType();
>   if (storage_class == DirectClass)
>     {
>       const PixelPacket
>         *pixel;
> 
>       pixel=getConstPixels(x_,y_,1,1);
>       if (pixel)
>         return(Color(*pixel));
>     }
>   else if (storage_class == PseudoClass)
>     {
>       const IndexPacket
>         *indexes;
> 
>       indexes=getConstIndexes();
>       if(indexes)
>         return(colorMap((size_t) *indexes));
>     }
> 
>   return(Color()); // invalid
> }
> -------------------------------
> 
> I am going to build a virtual machine and try different versions of ImageMagick to see if I can resolve this.
> 
> Regards
> 
> Steve
>

Yeah I've definitely noticed the sprinkled "#if"'s around imagemagick 
items and assumed the API changes have been a pain. I figured you would 
probably have a better approach but I figured I could at least figure 
out some form of resolution to help point you in a direction and utilize 
the functionality if needed :)

Let me know if I can be of any assistance (I'm pretty much on v6 for a 
while)

--Sean