[racket] Artefact when cropping and scaling an image

I'm not seeing what you're seeing, I think. Can you send a screenshot (or a
pointer to it)?

Robby


On Mon, Nov 18, 2013 at 5:59 PM, Daniel Prager <daniel.a.prager at gmail.com>wrote:

> Why does the following code generate visual artefacts along the right and
> bottom
> edges of the image?  How do I eliminate it?
>
> #lang racket
> (require 2htdp/image)
>
> (define (crop-to-aspect-ratio im final-width final-height)
>   (let* ([W (image-width im)]
>          [H (image-height im)]
>          [wh-ratio (/ final-width final-height)]
>          [w (* wh-ratio H)]
>          [h (/ W wh-ratio)]
>          [image (if (<= W w)
>                     (crop 0 (/ (- H h) 2) W h im)
>                     (crop (/ (- W w) 2) 0 w H im))])
>     (freeze (scale (/ final-width (image-width image))
>                    image))))
>
> (scale 5
>        (crop-to-aspect-ratio
>         (freeze (rectangle 259 356 'solid 'red))
>         40 56))
>
>
> Note that the two freeze instructions are essential -- the one in the crop
> routine
>  forces pixelation, which I want -- and the one in the calling code
> simulates starting with a bitmap.
>
> Thanks
>
> Dan
>
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