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Get rid of artifacts after png resize

asked 2020-03-22 09:54:29 -0500

borington gravatar image

updated 2020-03-22 12:36:11 -0500

Hello,

Having trouble to correctly resize a png image. For some reason getting black lines on edges where white area meets transparency. Used example from here (https://docs.opencv.org/master/js_geo...) Source Image:

image description

Code:

let src = cv.imread('canvasInput');
let dst = new cv.Mat();
let dsize = new cv.Size(408 * 2, 581 * 2);
// You can try more different parameters
cv.resize(src, dst, dsize, 0, 0, cv.INTER_LANCZOS4);
cv.imshow('canvasOutput', dst);
src.delete(); dst.delete();

Code above results in a resized image with a visible distortion image description

(Png is placed on a white background by default, it's easier to spot the issue this way)

To achieve better quality, I'm using an INTER_LANCZOS4 interpolation algorithm. Changing it to INTER_NEAREST helps to fix this particular image but then I'm losing quality for images with more details. Question is how to get rid of these black lines?

Thank you.

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answered 2020-03-22 10:28:54 -0500

mvuori gravatar image

You have tried the best and worst algorithms for generic use. The Laczos may have a problem, but most often the bicobic INTER_CUBIC is practically pretty much similar, so I'd try that. Indeed, photographers often use INTER_LINEAR, as it often holds details best when downsizing.

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Hi, thanks for the advice. With INTER_CUBIC, INTER_CUBIC, INTER_AREA I'm getting a similar result distortion is still visible INTER-CUBICINTER-LINEAR

borington gravatar imageborington ( 2020-03-22 10:40:51 -0500 )edit

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Asked: 2020-03-22 09:54:29 -0500

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Last updated: Mar 22 '20