On Mon, Apr 11, 2011 at 12:16 PM, geb a <ge...@yahoo.com> wrote: > Hello all, > > I'm having some trouble processing a block of pixels from an image. I want to > grab some portion of image, do something to it, and save it to a file. In > this example, I grab a portion of an image and save it to a file but the > image in the file is corrupted. Evidently I'm doing something wrong. I've > spent a number of hours trying to figure it out, but I'm blind to the > problem. I would be very grateful for any help someone can give me. > > Sincerely, > > Dan Anderson > > > #lang racket/gui > ; define the portion of the image I want to process > (define x 0) > (define y 0) > (define w 10) > (define h 10) > > > (define bm (make-object bitmap% "4colors.jpg"))
Use make-bitmap these days (but this doesn't seem to be the problem) > > (define pixels (make-bytes (* w h 4) 0)) ;each pixel has four numbers > (send bm get-argb-pixels x y w h pixels true) ; get the block of pixels > > pixels ;check that there is information in pixels > ;make a new bitmap of the section > (define nbm (make-object bitmap% pixels w h)) > (send nbm save-file "test.png" 'png) I think that doesn't do what you wanted. I think you need to call set-argb-pixels (the constructor is doing something with black & white pixels or something, not the same thing as get-argb-pixels). Robby _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
