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nfnt / resize

Pure golang image resizing
ISC License
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Resize the picture of the high deflection #21

Closed sb122k closed 9 years ago

sb122k commented 9 years ago

use:resize.Resize(100, 0, img, resize.Lanczos3)

sourece pic: image

out pic: image

Rotated 90 degrees, why

thanks

nfnt commented 9 years ago

Sorry, I'm unable to reproduce this using your input image and these parameters. My output picture is not rotated. Are you using the latest commit of this package? Internally the resizing algorithm has 2 steps: It scales horizontally then scales vertically. It seems that in your case the resizing stops after the first step. But there's no condition in the source code that would do that. Therefore I would need some more information on what's going on in your case.

ukautz commented 9 years ago

I can confirm the issue with JPEG images. However, at least with JPEGs, I think it's rather an EXIF issue.

Here is the original: http://pbrd.co/1q7lyW8 And here the thumbnail: http://pbrd.co/1q7ljKK

Looking at them in the browser -> both are rotated the same. However: the large one contains an EXIF Orientation flag saying Left-bottom. Every program (image editing, file browser, ..) which supports EXIF will display it rotated. My file browser (thunar, Linux) and the one from Apple both support EXIF in file preview. You should be able to confirm this by downloading both and either looking at them in your file browser preview or most image editing programs.. Anyhow: when processing the image with this library, it "seems" like a bug.. until you dig deeper.

So not sure if this classifies as a real bug, but it would be neat if one could keep the EXIF Orientation flag - or being able to set it (again: might not be the duty of a resize library).

nfnt commented 9 years ago

Right, the Go image package does not import/export EXIF metadata, therefore every information included in that data will be lost (see #13). A separate package would be necessary to handle metadata. @sb122k: Can you confirm that the issue might be caused by an Orientation flag in the EXIF data? I will close this ticket. If there is any indicator that the issue is caused by something different than EXIF data, I'll reopen it.

sb122k commented 9 years ago

sorry, long time no attention to this issue， I confirm that is the reason