Image Conversion: Changing JPEG quality

Anybody else is experiencing the same issues? (Opus 12.30 b8360)
Test cases here:

[Based on the old thread title.]

Failing in what sense?

What are you trying to do?

What is the error message or unwanted behavior?

From the screenshot, it looks like you're trying to convert JPEG files to JPEG format without making any other changes to them, which doesn't make sense.

As an example I tried to lower the quality to only 10%. Try to grab the files from the attachment see if it does something on your side. There is no error message.

OK, I've renamed the thread to make it clearer.

The image converter will not recompress JPEG files unless it needs to, as the aim is to avoid lossy compression degrading image quality unless required.

You can add the NOLOSSLESS argument to the command to override this, if you want to recompress JPEGs without making any other changes. (Note that it will also mean rotations are lossy.)

Alternatively, convert to BMP and then recompress to JPEG (if you don't need to preserve the EXIF metadata).

1 Like

Sorry don't get it. I could've sweared that it used to work, as I'm pretty sure I've done it dozen of times with Opus.

The JPEG itself is lossy unless set at 100% quality. I want to reduce the file size, and hence I'd like to have them at 70%, which cuts the size to 20% without any visible difference (tried it with another program, since Opus failed on me). I'm doing this on purpose, and I don't really need any safety check there. Otherwise I'll need to employ some other program like XNConvert which is a pain, since I need to do it over 19 directories (for this particular case), which should be a one-way pass with Flat View option.

JPEG is lossy even at 100%. Every time you recompress a JPEG, even more image quality is lost (even at 100% quality).

The image converter in Opus has always avoided doing lossy recompression of JPEGs unless required (e.g. due to resizing or cropping the image, or rotating when the image isn't suitable for lossless rotation).

If you add the argument I mentioned, it will override this and let you recompress JPEGs.

Not too intuitive, but at least it's working. Thanks again. :slight_smile:

The aim is to protect people from degrading image quality unless they really, really want to.

But we will be adding a checkbox for that argument in the future, to make it easier to override.

1 Like

Thanks Leo, I bet this will be just fine. I sincerely thought there was something wrong with the program.

Directory Opus users are usually the ones that are looking far more from a file manager than common Windows users, so I believe we're more aware of what we really do. :slight_smile: