Cropped image dimensions by 30% is like 5% less size on memory

[ghost]

note: I know the main purpose of this, is to smart crop, and this is already great. Still I have another problem

Context

I want to use this amazing library for uploads in browser. I tried to grab code from testsuite and it works fine.

Unfortunately I find in most cases:

Problem

cropped size in px / original size in px

is always way less than

cropped size in mb / original size in mb

I wished smartcrop.js would let the image quality as is, in this case I think size on memory would drop relatively to the cropped size ( logically as images are raw data? ).

Thanks a lot !!

[ghost]

I wished size would drop relatively as smartcrop is intended also for optimizing size. that would be great !

[jwagner]

Hi @bacloud14,

I'm not sure what you mean. smartcrop.js does not do anything to image quality nor does it do image compression - or anything else - to the image. It just gives you candidate crops. The test suite just draws on . It doesn't do image compression either.

Could you provide a bit more background on what you mean?

[ghost]

ok, I tried that "guitarist.jpg" file, cropped with var options = { debug: false, width: 250, height: 250 };

The result image of type 'png' with these observations:

guitarist.jpg is 427 * 640 px
canvas.png is 250 * 250 px

while
guitarist.jpg is 170KB
canvas.png is 146KB

I thought canvas.png would much less in file size.

Something near : ((250 * 250) / (427 * 640)) * 170 = 38.87 KB

[ghost]

Like when you take a paper, crop it with scissors, the amount of paper is always the same relatively to size.

[jwagner]

You are really comparing apples and oranges here. PNG and JPEG compress data differently. PNG is generally a quite bad choice to compress photographs. Maybe https://developer.mozilla.org/en-US/docs/Web/Media/Formats/Image_types#choosing_an_image_format or https://www.freecodecamp.org/news/best-image-format-for-web-in-2019-jpeg-webp-heic-avif-41ba0c1b2789/ help you understand that a bit better.

But that really doesn't have anything to do with smartcrop. Smartcrop doesn't produce jpegs or pngs - it just gives you crops.

[ghost]

Probably I mistakenly change the name of the output file to PNG.
So I assume crop doesn't change extension I mean I'm sure now.
Anyway, my question was clear on why the crop size is not relative to the new size.
Anyway closing this as I seem not to be presenting the idea well. Thanks.