[magick-users] perl pixel manipulator

[arcanaimperii at imagemagick.org]

> multi-megapixel images, doing it a pixel at a time would be
> intolerably slow.

Modern versions of PerlMagick incudes the GetPixel()/SetPixel().  An efficient
access method would be to grab and update one image scanline at a time.  To
change a single pixel, use

  @pixels=$image->GetPixel(x=>1,y=>1);
  $pixels[0]*=0.5;
  $image->SetPixel(x=>1,y=>1,color=>\@pixels);