I have two images with the same dimensions. One is a facebook icon and the other is a plain white image. They are 32 bit, 128 pixels by 128 pixels, 96 pixels per inch and 3.39 cm but one is 1.87kb and the other is 50kb. Both are png format.

I want the second image to be as small as the first one but even with compression, the least size I can get is 3kb. I have tried removing other details like dates, orientation to achieve the smallest size but sometimes the size even gets a little bigger.

enter image description hereenter image description here

  1. Why is it that these images are of different sizes on disk yet they have the same properties and attributes?

  2. How can I make my image as small as the first one?

  • 9
    \$\begingroup\$ I'm voting to close this question as off-topic because it is about file compression methods, not photography. \$\endgroup\$
    – Tetsujin
    Mar 22, 2018 at 10:28

2 Answers 2


You can't. Not with a lossless format like PNG.

Image compression depends on the amount of information in an image, ie. the detail present. A square of a solid blue contains little information and can thus be described simply (as i did here). If i were to describe the Mona Lisa to you, i'd need a bit more than five words. Software compression works the same way, a simple logo with large features of solid colours compresses better than a more complicated image.

Lossy compression, OTOH, like found in JPEG images, could compress both to the same size, by either wasting space on unnecessarily high quality for the first, or dropping fine details from the second image.

Another option would be an uncompressed format like BMP, which only depends on pixel dimensions and bit depth. Those will always be the largest files, though.


You need a smarter program. More info about png,


if you have 128 by 128 pixels then your image itself has 128^2 or 16,384 pixels.

If you use 32 bit colour that's 4 bytes per pixel you get 64K bytes.

On the other hand, if you used indexed color, you need a dozen or so bits per colour for the color table then, for 2 colour you need 1 bit per pixel. 1 bit per pixel is 2K uncompressed.

Look to see of your editing software allows you to change the bit depth of the image and use indexed colours.

So after the downvote, I tried it. Photoshop PS 6 gets it down to 4k. But opening the original and saving a copy is also 4K. So PS6 isn't great.

https://compress-or-die.com/ gave this result

Compress or Die version

Size 685 Bytes.

That was the first online compressor I tried.


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