XnView Software

I am trying to reduce the size of a cbz file by cracking it and then reducing the size of the jpegs inside. However, sometimes when I try to shrink the images they end up larger. For instance I set them to reduce to 50% of the original size using Lanczos but they end up being twice as large. So a jpeg that is 4MB in size will end up being 8MB in size after resizing.

Are there settings I can use that will result in a 50% exact reduction in size of all images when I set resize to 50%? Or am I missing something? I would like to reduce a jpeg from 4MB to 2MB without losing much in the way of image quality.

Welcome aboard, Tec4.

Could you please upload a sample to a free file sharing host like Wikisend? (The forum's maximum attachment size is 2 MiB.)

Thanks, I enjoy using the app. Do you want a sample of the resized image?

Tec4 wrote:Do you want a sample of the resized image?

Sorry, I should've been more clear: I'd like to do some tests on one of the 4MB originals so I can hopefully give you the best JPEG compression settings for your use case.

Couldn't get wikisend to work but here is a zippyshare file:

http://www55.zippyshare.com/v/XWezsmY4/file.html

Thanks for the sample. Please try the following settings:

Wow that worked nicely. Although it ended up smaller than 50%. But smaller is actually better so I'll take it. Thank you!

Tec4 wrote:Although it ended up smaller than 50%. But smaller is actually better so I'll take it.

Here are the geeky stats in case you're interested

• Original
  • Dimensions: 3975×3056 pixels (100%)
  • Chroma subsampling: 4:4:4 (1×1,1×1,1×1)
  • Quality factor (approximated): 90
  • File size: 3'983'972 bytes
  Result
  • Dimensions: 1988×1528 pixels (50%)
  • Chroma subsampling: 4:4:4 (1×1,1×1,1×1)
  • Quality factor: 90
  • File size: 1'301'058 bytes

Interesting...thank you.

XnTriq wrote: Thu Aug 31, 2017 12:45 am Thanks for the sample. Please try the following settings:

144849_1.png
144849_2.png
144849_3.jpg

Why do you have to even use resize? When I put my output settings to 80 or 90 the file size shrinks tremendously> I don't understand why the resize is even needed.

DoubleD wrote: Thu Sep 15, 2022 10:34 pmWhy do you have to even use resize? When I put my output settings to 80 or 90 the file size shrinks tremendously> I don't understand why the resize is even needed.

Resize is optional. It depends on how much you want/need to reduce the file size.

XnTriq wrote: Tue Sep 20, 2022 10:15 pm Resize is optional. It depends on how much you want/need to reduce the file size.

Thanks - I reduce to 70% and it seems OK for facebook. Sure make the upload go faster.

I may try playing around with the resize option but for the life of me I can't figure out what it really does.

I know my picture are usually width: 6192 and height of 4128 Every time I crop and Image I always try to resize back to those values or as close as I can possible get. I have noticed in the past that after cropping my photos seems smaller (visually) that the ones that I didn't crop (especially after uploading them back to facebook). See example the circled photos

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  2022-09-20 19_32_07-(1) Facebook — Mozilla Firefox.png (283.29 KiB) Viewed 2837 times

DoubleD wrote: Thu Sep 15, 2022 10:34 pmWhy do you have to even use resize? When I put my output settings to 80 or 90 the file size shrinks tremendously> I don't understand why the resize is even needed.

Images have pixel dimensions, and the dimensions of images from modern cameras may be much larger than required for many, such as web display, needs. In your case it depends on whether the images uploaded will be viewed directly on the screen in a web browser, or downloaded and possibly archived to be viewed again in the future, when screen quality may be better. In general, for many purposes the pixel dimensions of modern camera photos can be substantially reduced with a substantial reduction of fie size, important on the web.

Viewing an image that has much larger dimensions than the screen used will not result in a significantly higher quality display. However, screen pixel dimensions vary and tend to increase with time, and a higher resolution image could be better when an image might be viewed zoomed-in. When reducing image dimensions it is generally best to reduce dimensions by a power of two, such as 50%, 25% for example, as the resulting downsized image could have better quality, although for the above reasons the benefit may not be noticeable in practice.

It is important to distinguish between the Resize, the action you need, and the Canvas resize action, which are provided for different uses and may, depending on the settings used, produce different results. In XnConvert the Preview function enables the effect of the selected actions to be seen.