SFML community forums
Help => Graphics => Topic started by: guyyst on February 25, 2016, 07:44:09 pm
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When I rotate an image using the Windows explorer context menu options "Rotate left" or "Rotate right" the new image rotation is not picked up by SFML if it's a JPEG. The image is simply loaded in its original orientation.
This problem is not present with PNG or BMP files.
Out of curiosity I compared the original and rotated versions of both PNG and JPEG files in a hex editor and found that the bytes indicating the image resolution are indeed flipped for PNG but not for JPEG.
This leads me to believe that the problem lies more within Windows than SFML, but still raises the question why other programs, like paint.net and Photoscape, are able to detect the rotation.
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I guess that for JPEG, Windows uses the EXIF orientation (a metadata field) instead of actually rotating the whole array of pixels. All image viewers decode and apply the EXIF orientation, SFML doesn't.
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Yeah I didn't think to check if there's an EXIF tag for orientation. Libexif works just fine for reading that so I guess I can just apply the rotation myself. Thanks for the answer :)
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Or you could just actually rotate the image once and for all in some image manipulation program like Gimp (https://www.gimp.org/) or Photoshop (http://www.photoshop.com/) (or something else) and then just use that rotated image...
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Or you could just actually rotate the image once and for all in some image manipulation program like Gimp (https://www.gimp.org/) or Photoshop (http://www.photoshop.com/) (or something else) and then just use that rotated image...
Well this program is to be used as an image Viewer, so the whole point is to be able to handle and read any form of manipulation made to the image.