[Haskell-cafe] Hsmagick crash

[Mark Wassell]

Have you tried 
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/pngload ?

Mark


Ron de Bruijn wrote:
> Hi,
>
> I am trying to extract the image data from various file formats and it 
> appeared that hsmagick would be the right package to use.
>
> However, it doesn't actually work or I use it incorrectly. If you have 
> installed hsmagick and change the value of some_png_file to some 
> existing png file, you should see that it crashes at some random 
> pixel. For the particular 256*256 image I had, it crashed on pixel_nr 
> `elem` [54,56,57].
>
> I am open to suggestions for better ways to get a Array (Int,Int) RGB 
> from e.g. a png file.
>
> import Graphics.Transform.Magick.Images
> import Graphics.Transform.Magick.Types
> import Foreign.Storable
> import Control.Monad
>
> image_file_name_to_2d_array file =   do
>     himage <- readImage file
>     let ptr_to_image = image himage
>     himage_ <- peekElemOff ptr_to_image 0
>     let bounds@(_rows, _cols) = (rows himage_,columns himage_)
>         number_of_pixels  = fromIntegral _rows * fromIntegral _cols
>     mapM (\pixel_nr -> do
>            putStrLn ("Pixel: " ++ show pixel_nr)
>            pixel_packet <- liftM background_color_  $
>              peekElemOff
>               ptr_to_image
>               pixel_nr
>            let red_component = red pixel_packet
>            putStrLn ("Pixel packet: " ++ show red_component)
>            return red_component)
>       [0.. number_of_pixels - 1]
>
> some_png_file = "foo.png"
>
> t = do
>   initialize_image_library
>   image_file_name_to_2d_array some_png_file
>
> initialize_image_library = initializeMagick
>
> Best regards,
>  Ron de Bruijn
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