XnView Software

When aspect ratio information is present inside PNG, TIF, JPG, BMP etc image files, XnViewMP will show both the thumbnail and the preview with incorrect proportions. Only after you open the image that it will be shown with its correct aspect.

Note: For GIF files, the image will still be shown with incorrect aspect ratio even when you open the files.

Use the following images to test the problem. They can be converted
http://frs.badcoffee.info/images/Zarth-PC88.png
http://frs.badcoffee.info/images/gifsui ... tratio.zip

Tested with XnViewMP 0.81 on Mac OS-X 10.10.5.

O.k., thank you, I can also reproduce the problem. Issue 950 is fixed in next version.

This problem is supposed to be fixed in XnView MP 0.85 beta 1. Please check and confirm the bug fix here.

As requested, I tested the embedded aspect ratio bug with 0.85beta2 (Mac) and it's still present.

The files to test the problem can be found in the links bellow:

http://frs.badcoffee.info/images/Zarth-PC88.png
http://frs.badcoffee.info/images/gifsui ... tratio.zip

sd_snatcher wrote: http://frs.badcoffee.info/images/Zarth-PC88.png
http://frs.badcoffee.info/images/gifsui ... tratio.zip

Preview is always incorrect?? or only the thumbnail?

I just tested with XnView-MP v0.88 on Mac OS-X. These are the results:

1) Preview

The aspect ratio is shown correctly for JPG and PNG files. It is still incorrect for GIF files.

But there's a catch: ideally, the image should only be expanded to adjust the aspect ratio, so no pixel information is lost. But XnView is expanding them for changes in the vertical axis, and reducing them for changes in the horizontal axis.


2) Thumbnails in the file browser

The aspect ratio is incorrect for JPG, PNG and GIF files.


To help with the tests, I attached here three files with the same image saved in JPG, PNG and GIF formats. They all have the Pixel Aspect Ratio field set up inside them. In all cases, a black square should be rendered and all images should render the square with the same size.

- If a rectangle is seen, then the aspect ratio info isn't being respected.
- If the size of the rendered rectangle differs between all the rendered versions, then the Aspect Ratio scaler isn't scaling the axes by the same factor.

The formula for the GIF pixel aspect ratio can be seen at this link. It goes like this:

In a nutshell, it goes like this:

1) The Gif Aspect Ratio field is present at the offset +12 of the file.

2) The formula for the Pixel Aspect Ratio is this

- If HeaderAspectRatio = 0, then no Pixel Aspect Ratio is defined
- When HeaderAspectRatio > 0, PixelAspectRatio = (HeaderAspectRatio + 15) / 64

Thanks to your detailed description I can reproduce the problem.

It seems that some Pixel Aspect Ratios are still not shown correctly by XnView. Like the one in this attached image.

See issue for current status and some details.

This problem is supposed to be fixed in XnView MP 0.91. Please check and confirm the bug fix here.

I just tested with XnView-MP v0.91-Beta4 on Mac OS-X. These are the results:

1) Preview

The aspect ratio is shown correctly for JPG, PNG and GIF files now.

But this problem still happens: "ideally, the image should only be expanded to adjust the aspect ratio, so no pixel information is lost. But XnView is expanding them for changes in the vertical axis, and reducing them for changes in the horizontal axis."

I attached a screenshot showing that 2:1 is being rendered much smaller than 1:1 and 1:2 on image view. But they should all be rendered at the same size.

2) Thumbnails in the file browser

The aspect ratio is still incorrect for JPG, PNG and GIF files, as show the attached screenshot.


To help with the tests, I made this page with a set of images. In all cases, all images of the same set (Lennas or squares) should be rendered with the same size.

sd_snatcher wrote: ↑Sat Aug 04, 2018 3:18 am To help with the tests, I made this page with a set of images. In all cases, all images of the same set (Lennas or squares) should be rendered with the same size.

where is the download link for images set?

The images can be downloaded directly from this page, with right-click:
http://frs.badcoffee.info/PAR_AcidTest

To make things easier, I also attached it here.

Are you sure that you have 'rebuild thumbnails'?

for preview, 512x256 & 256x512 should be expanded as 512x512 or 256x256?