1.6.1 Unsharp/blurry picture zoom out

[Smeeta]

I haven't seen that the update 1.8.5 has already been released, but I've tried again after I updated to this new version and it still shows the same problem.

I've cropped an example image here which is 8bit based:
https://www.dropbox.com/scl/fi/9g1xy4go ... wz8wu&dl=0

And for comparison also converted it to 24bit here:
https://www.dropbox.com/scl/fi/vjk6kd75 ... e2ym9&dl=0

I've also made a .gif to compare each other while opened in XnView:
https://www.dropbox.com/scl/fi/n6m4h8y8 ... 176bw&dl=0

Both of the cropped files look the same in other image viewers, but in XnView (hence the .gif example) the 8bit looks quite blurry compared to the 24bit.

[xnview]

I haven't seen that the update 1.8.5 has already been released, but I've tried again after I updated to this new version and it still shows the same problem.

Ok, could you send me the picture file used? Always with Lanczos4/Bilinear filter?

[Smeeta]

This is the original image (I'm sorry for ogling your eyes out ).
https://www.dropbox.com/scl/fi/maqch5zg ... knhkg&dl=0

Using Lanczos4/Bilinear in different variations in 'Zoom in' & 'Zoom out' settings, if necessary I've already linked my xnview.ini file for bug fixing in my original thread:
viewtopic.php?p=203339#p203339
Just in case when it's also going to be needed.

[user0]

there are few issues

0. have 2 PNGs: 8bit palleted and resaved as 24bit (20 colors)

A - antialiasing as reported above
1. set antialiasing to any filter except Bilinear in Settings
2. open image, zoom-in or zoom-out (effect with zoom-out is harder to notice)
3. switch between images
filter effect will be different for 24bit image (only Bilinear filter affects both images in the same way)

B - navigator
1. zoom-in to make navigator appear
2. switch between images
3. (optional) resize navigator window
24bit image will have more artifacts in nav window

8_24_png_view_antialiasing_and_navigator.gif (117.61 KiB) Viewed 1812 times

[xnview]

Thanks to your detailed description I can reproduce the problem.

[xnview]

This problem is supposed to be fixed in XnView MP 1.8.6. Please check and confirm the bug fix here.

[user0]

I don't see any improvement in 186

[Smeeta]

This problem is supposed to be fixed in XnView MP 1.8.6. Please check and confirm the bug fix here.

I also can confirm that version 1.8.6 doesn't improve on the bug as user0 already mentioned (at first I thought it was on my end again, but thank you for the clarification).

[xnview]

I also can confirm that version 1.8.6 doesn't improve on the bug as user0 already mentioned (at first I thought it was on my end again, but thank you for the clarification).

But its not fixed for the image displayed too??

[user0]

8bit is blurry and shifted to the top left by 1px with all filters except Bilinear,
eg Lanczos 4 at zoom 400%:

186_8_24_png_antialiasing-lanczos4_and_navigator.gif (119.42 KiB) Viewed 1450 times

[xnview]

Lanczos & bilinear dont use same process, and you can have small difference. But i means the original problem, blurry when 8bits and not in 24bits?

[user0]

Lanczos & bilinear dont use same process, and you can have small difference. But i means the original problem, blurry when 8bits and not in 24bits?

OP's issue is with zoom-out filters, but imo zoom-in is easier to test
I compare 1filter against 2images (8bit-indexed and 24bit), not filter vs filter

tests
0. win dpi scale - 100%
1. open test image
2. zoom to 400%
3. select zoom-in filter
4. make screenshot (24bit png) and crop accordingly
5. repeat for each variant and compare with Beyond Compare or by eye as difference is very noticeable

results
Bicubic, Spline and Lanczos filters make 8bit-indexed (comparing to 24bit):
1. much blurrier and
2. shifted to the top left corner by 1px

test_img+results.zip

(393.73 KiB) Downloaded 57 times

ps. I assume filter:none = Nearest neighbor ?

related
1.8.0 - viewer - High zoom quality - few issues

[xnview]

reopened

[xnview]

This problem is supposed to be fixed in XnView MP 1.8.7. Please check and confirm the bug fix here.

[user0]

fixed in 187