From: nicolas Date: Thu, 7 Oct 2010 00:07:53 +0000 (+0000) Subject: clearer Lanczos2D comments X-Git-Tag: 7.0.1-0~8737 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3073181f51fb4113215af16761678c0ecf7c187f;p=imagemagick clearer Lanczos2D comments --- diff --git a/magick/resize.c b/magick/resize.c index 223abeca7..70623275e 100644 --- a/magick/resize.c +++ b/magick/resize.c @@ -927,20 +927,21 @@ MagickExport ResizeFilter *AcquireResizeFilter(const Image *image, * line (equal to 1, say, on a black=0 background) is exactly * preserved when no-op is applied to the image. It also * ensures that---with no-op---the nearest two columns on - * either side are minimally changed. Specifically, nearest - * columns on the left and the right are raised to c from - * zero, and the second closest columns on the left and right - * are lower by c from 0. (Hence, the closest columns are made - * slightly positive, and the second closest are made slightly - * negative, equally.) All the other columns are - * unchanged. The size c of this blur/ripple is .002042317 + * either side are minimally changed (the farther columns are + * unchanged). Specifically, nearest columns on the left and + * the right are raised to c from zero, and the second closest + * columns on the left and right are lower by c from + * 0. (Hence, the closest columns are made slightly positive, + * and the second closest are made slightly negative, in equal + * amounts.) The size c of this blur/ripple is .002042317 * (about one fifth of one percent). Consequently, this choice * of scaling of the support of the standard Lanczos2D * preserves "contant on columns" images with values between - * -1 and 1 to within .00817 (within one percent). + * -1 and 1, to within .00817 (within one percent). * - * This special scaling was discovered by Nicolas Robidoux of - * Laurentian University. + * This special scaling of the standard Lanczos2D kernel in + * the context of Elliptical Weighted Average resampling was + * discovered by Nicolas Robidoux of Laurentian University. * * resize_filter->blur, below, is 1/s. */