Crop region and image resolution: a dilemma about final image file sizes

The right place to speak and share about your experiences of GraphicConverter
Post Reply
360design
Posts: 3
Joined: Fri Oct 18, 2019 9:48 pm

Crop region and image resolution: a dilemma about final image file sizes

Post by 360design »

Dear GraphicConverter devs,

I love GC because it's the only app I know that will do something that saves me a lot of time: batch conversion/modification of specific region of images. My work is to prepare materials for online courses of a big university and I often have to design tutorials, lessons, etc. So I deal with a huge amount of images and those images most of the time need to be cropped. So I long ago have started to rely on GC to do help me out. I set Convert & Modify as follows: specific file type / select use batch + www ready / Crop Region with the proper perimeters and hit Okay. Works like magic! My experience has always been cropping smaller areas thus I ended deleting large portions from the originals, and I could see that the final file sizes would be smaller when in comparison with the source files. But recently I've been cropping some files that just need cropping of the image borders and I noticed that the final files sizes remain about the same size of the originals or even a little larger. A file that is 1.2M sometimes become 1.3! I have even tried deselecting XMP/ICC profile (Interlaced and Filter are always set to none) but that didn't change anything. As a way to compare, I cropped a file using MacOS Preview app and the final file was about 617KB. Cropping the same image using GC I got 901KB and also 896KB (after playing around with XMP/ICC profile selecting/deselecting). I am at a loss and the necessity to crop images is not just a matter of design but also to make the files lighter and smaller. I cannot decrease the quality of the images or shrink them. Ideally I'd need to just crop out what I don't need and keep the quality of what I'm preserving to keep it just as the same as in the original file. More or less like the result achieved with the Preview app I aforementioned. Can you please help me with this matter?

I read this topic and it seemed to be dealing with similar issue as mine (viewtopic.php?f=3&t=6106) but I don't know if the same solution applies (plus I don't know if "fat file" is really the description for what I'm chasing here). As I said: I need the image quality and resolution to remain the same as in the original but it's obvious that file size will decrease if I'm deleting portions of picture. Thank you!
User avatar
forum_adm
Site Admin
Posts: 1814
Joined: Fri Dec 23, 2016 9:41 am
Location: Germany
Country: Germany
Contact:

Re: Crop region and image resolution: a dilemma about final image file sizes

Post by forum_adm »

Hi,

please click onto the options for the save format.

Which JPEG quality is chosen?

Thorsten
Screen Shot 2019-10-19 at 09.59.jpg
Screen Shot 2019-10-19 at 09.59.jpg (364.6 KiB) Viewed 4384 times
360design
Posts: 3
Joined: Fri Oct 18, 2019 9:48 pm

Re: Crop region and image resolution: a dilemma about final image file sizes

Post by 360design »

Thank you for replying.

I don't save in JPEG but PNG.

What are the best specs for PNG save?

If I switch Quality to 75, won't I be losing in resolution/definition?
User avatar
forum_adm
Site Admin
Posts: 1814
Joined: Fri Dec 23, 2016 9:41 am
Location: Germany
Country: Germany
Contact:

Re: Crop region and image resolution: a dilemma about final image file sizes

Post by forum_adm »

Please select this for PNG:
Screen Shot 2019-10-20 at 14.04.jpg
Screen Shot 2019-10-20 at 14.04.jpg (109.63 KiB) Viewed 4371 times
360design
Posts: 3
Joined: Fri Oct 18, 2019 9:48 pm

Re: Crop region and image resolution: a dilemma about final image file sizes

Post by 360design »

Thank you so much, forum_adm! Worked like a charm!

My version of GC doesn't have that Special box on the PNG settings menu, but I think the trick was to select Automatic on the Filter list because after doing that 1.1MB images were converted to 625KB files. The files I recently converted with GC using the settings you indicated ended up being "slimmer" than the versions I had cropped with Preview (and that had never happened before). Doing a side by side comparison of both versions, I see no apparent loss or any degradation of quality although both versions (GC's and Preview's) still differ in size. Do you know why that happens? And I don't wanna take too much more of your time, but can you please explain to me why an Automatic filter is better than None? I thought that by using None files would always be lighter - after all "none" implies that no additional changes are being made to a file - and that Automatic, or any other type of filter, would add an extra "layer" to the image.

Also: as for the files that I previously converted before leaning the Automatic filter trick, is there anything I can do to get them into a smaller file size? Unfortunately I deleted the source files and cannot just re-convert them all over again. The "cropped versions are still larger than the original raw files. Is there anything I can do with GC to get them lighter without losing quality?
User avatar
forum_adm
Site Admin
Posts: 1814
Joined: Fri Dec 23, 2016 9:41 am
Location: Germany
Country: Germany
Contact:

Re: Crop region and image resolution: a dilemma about final image file sizes

Post by forum_adm »

The PNG format is by default lossless.

You can try to use ImageOptim in addition.
Post Reply