1) I've changed my data representation of the output of MagickExportImagePixels from a binary matrix of 0's and 1's to a representation of just the black pixels as a list of rows, the black pixels in each row represented by a pair giving the start and end column positions of a contiguous black pixel strip. I.e. '((row (black-pixel-strip-start-pos . black-pixel-strip-end-pos) ... ) ...) This cuts the memory usage down immensely (at least 30 to 1) and in fact simplifies my code, since I eventually produce a graph of connected pixel strips with the pixel strips represented as above with pointers added to other connected black pixel strips.
So Pierpaolo thank you, but I wont be needing a bit vector package after all. 2) On Fri, Jul 20, 2012 at 10:53 PM, Eli Barzilay <e...@barzilay.org> wrote: >you can just create a > byte string of the appropriate size, then use it directly. For > example, I added this: > > (defmagick* MagickExportImagePixels : > _MagickWand (x : _long) (y : _long) (width : _ulong) (height : _ulong) > (map : _string = "I") (storage-type : _StorageType = 'CharPixel) > (block : _bytes = (make-bytes (* width height))) > -> _status > -> block) > > (It's a bad hack, since it calls the function > `MagickExportImagePixels' but it really hard-wires the `map' and > `storage-type' arguments...) Yes, MagickExportImagePixels uses the exact same interface as "MagickGetImagePixels" and again yes it is the intensities and only the intensities I export. Is this slightly less of a hack but more importantly will it work. If I add this to the ImageMagick FFI (defwand* MagickExportImagePixels : _MagickWand (x : _long) (y : _long) (width : _ulong) (height : _ulong) (map : _string) (storage-type : _StorageType) ;; create the block, remember size and type (size : _? = (* width height (string-length map))) (type : _? = (StorageType->type storage-type)) (block : _pointer = (malloc size type)) -> _status -> block) So I can use it to produce the byte-string of intensities for this application, but also leave its generality for other applications and if I need to for other applications I can then also create a wrapper function that calls this but takes its output and produces a list of lists as you originally had it do. Thanks, Harry Spier ____________________ Racket Users list: http://lists.racket-lang.org/users
