PNG File Becomes Larger after Resizing to Half?

Questions & Suggestions
1

Surprised to see that the image file becomes larger after resizing to half. Why? Any fix? @peternlewis

Macro:
image

Before (128x128, 4KB):
image

After (64x64, 6KB):
image

2

Hi @martin.

Out of curiosity I tried your experiment and came up with a conclusion for you.

This is the macro I used:
KM 0 2021-03-08_23-32-24

and this is the result:
KM 1 2021-03-08_23-33-40

As you can see I got the result that you hoped for.

My conclusion is this: I used the System Clipboard whereas you used a named clipboard. I have seen in a number of posts that named clipboards sometimes behave "differently". So could this be the cause?

Just food for thought...

1 Like
3

Interesting. I tried it with SystemClipboard, no difference.

Can you try the same one I use? see attached.emoji_u00a9 emoji_u00ae emoji_u1f0cf

4

OK - so I tried with your image and got your (confusing) result!

KM 2 2021-03-09_01-06-40

Loading up your images in GraphicConverter I see that the first one is compressed at 1:24 while the second one is compressed by 1:3 which is why the second (smaller) image is a much larger file. (With my images, the compression was 1:11 and 1:6 so the smaller difference between their compressions still led to them being the expected, intuitive sizes.)

I have no idea how the compression is determined by KM - that's perhaps something for @peternlewis to answer.

1 Like
5

It doesn't get smaller because there isn't less information.

When you scale it like this, you are adding a whole bunch of shades.

The images are not big enough for the reduction in size to result in an overall reduction in storage space.

For example if you just do this with Acorn, loading the image, saving it as a png, scaling it to half size, and saving it to png you get:

6492 - 128x128
6821 - 64x64

Note that for Acorn too, the half size image is larger than the full size image.

Look at the histograms of the two:

image image

Note all those extra spikes in the scaled image, they result in more information being required to store the image.

On top of that there is a whole bunch of extra data in there that isn't related to the size of the image and does not scale when you reduce the size of the image.

2 Likes
6

Thanks, Peter.

I found an app that could compress the images without changing the size. I guess this kind of app is the right tool for reducing the storage space. This kind of tool can be used together with the resizing tools to both reduce the size and the storage space.

7

Recommend ImageOptim for compressing images. (It's free)
As I showed in the OP and Peter in his reply, using the resizing image action is not able to reduce the size of small images.
I tried ImageOptim to compress these icons I downloaded from the internet, after the compression, it's storage space is down from 6kb to 933bytes.

image

1 Like
8

Hey Martin,

See this thread: PNG Optimizer

-Chris

1 Like
9

Thanks a lot @ccstone.
It's interesting ImageOptim only compresses about 10% of the number of images I dragged into. I have to re-drag and re-drag the 90% images back to it for it to compress another 10%... That macro seems very powerful to me!

10

Hey Martin,

Take note of this too:

-Chris

1 Like
11

ImageOptim

Just a note: In Preferences you can adjust the image quality and processing speed, in exchange of longer or shorter processing times depending on your settings.

1 Like
12

Watched a tutorial on ImageMagick, looks like it is very powerful. I probably need more time on it to be able to use it comfortably. Thanks a lot for recommending it!

1 Like
13

Yes. I noticed that too.

1 Like