v4.23 Change to image resolution is no longer saved!

[kirchh]

Earlier versions of IV would immediately change the resolution data in the image file when the user changed those values in the Image Information dialog. In the current version (I'm running 4.23), changes to the image resolution are being discarded.

Thanks --
--Daniel

[Sam_Zen]

Do mind that this resolution is about the DPI, so no changes to the bitmap itself.
This seems a bit buggy though. Can't recall how earlier versions did, but with a JPG a change is indeed not kept. Next time it's back to the default 100 x 100. While GIF and PNG start each time with empty values.

[kirchh]

Do mind that this resolution is about the DPI, so no changes to the bitmap itself.

Exactly -- that's why the image did not need to be re-saved after making a resolution change; no need to go through another generation of compression (in the case of JPEG, for example). But in the current version, this no longer works, so it seems to be a clear bug.

--Daniel

[Bhikkhu Pesala]

It is no different to IrfanView 3.97 — I don't know about earlier versions.

[kirchh]

It is no different to IrfanView 3.97 — I don't know about earlier versions.

I think I was running 4.10 previously.

--Daniel

[pixperson]

bug confirmed, DPI is discarded. Setting H & V DPI is useful.

Confirming this bug, based on my experience.

Setting the DPI (pixels/inch) is a useful capability.

My scanner generates GIF and JPG files with H and V DPI set to zero or incorrectly.
When I email them to others, some novice (graphics) users have problems because some programs do not print them correctly.

kirchh -- I do not understand why changes to the header area should cause JPG re-compression, a bad thing.
The existing JPG binary data can be copied as-is, bit for bit.

Changing this (or any other file header or EXIF info) should be a "lossless" change to the file header.

Thank you

[kirchh]

kirchh -- I do not understand why changes to the header area should cause JPG re-compression, a bad thing.

They shouldn't, and in previous versions, the image did not need to be re-saved for changes in resolution to take effect. Now, however, it seems that the image must be re-saved, and unless there is a special case check in the save code that makes a (silent) exception, the image will be subjected to whatever format/compression is selected.

--Daniel

[Bhikkhu Pesala]

Irfan says it has always been like this.

The DPI in image->info won't change anything in the file, ONLY after you save the image as file. Same in ALL versions.

Maybe the guy mixed the lossless JPG dialog with image->info?