How to resize an uneven image (different width, height) to a fixed size image?

Asked Jun 24 '22 at 10:34

Active Jun 24 '22 at 10:59

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I have a dataset containing images with variable widths and heights. I want to resize them to a fixed size, e.g., 128 x 128 for my model. I can resize using PIL like

Image.resize(size, Image.ANTIALIAS)

Image.thumbnail(size, Image.ANTIALIAS)

The problem is that when the image width or height is smaller than 128px, these approaches dont resize the image to the desired size as they need to maintain the aspect ratio. I observed the same behavior with ImageOps.contain().

Is there a better way to resize the images to a fixed dimension while maintaining the aspect ratio using python or pytorch (transforms.Resize() in this case squashes the output)?

edited Jun 24 '22 at 10:59

asked Jun 24 '22 at 10:34

Ammar Ul Hassan

I think this is answered here https://stackoverflow.com/questions/2232742/does-python-pil-resize-maintain-the-aspect-ratio, using the thumbnail method. – Beatdown Jun 24 '22 at 10:37
normally, do a padding before resizing should be nice – dtlam26 Jun 24 '22 at 10:38
@Beatdown Thumbnail has the same behavior. For example, if the image size is 185x57, after the operation it gives me 128x39. – Ammar Ul Hassan Jun 24 '22 at 10:40
hmm okay, did you try 'contain' e.g. image = ImageOps.contain(image, (2048,2048))? – Beatdown Jun 24 '22 at 10:42
@Beatdown Nope, I haven't tried it. – Ammar Ul Hassan Jun 24 '22 at 10:44
Give it a go, it's on the same page I linked earlier. – Beatdown Jun 24 '22 at 10:45
@Beatdown I just tried 'contain' it gives me 128x39 (same behavior). – Ammar Ul Hassan Jun 24 '22 at 10:51
@dtlam26 for the padding way I am thinking about the boundary pixels? they may affect the model training. – Ammar Ul Hassan Jun 24 '22 at 10:53
actually not, jitter image does not affect the model training much as you only pad the image to square by extending width/height. A lot of new model training have applied this way though. 0 padding – dtlam26 Jun 24 '22 at 11:11
@dtlam26 So should I pad it to some large size (greater than 128 in my case)? and then crop the 128x128 from the center? – Ammar Ul Hassan Jun 24 '22 at 11:15
@AmmarUlHassan you can pad it to a square image (185x57) to both x axis (185x185) and resize that square image to 128x128 – dtlam26 Jun 24 '22 at 12:30

How to resize an uneven image (different width, height) to a fixed size image?

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