resolution - How big is an 800x600 image file in PNG?

07
2014-07
  • Tyler Durden

    How big is an 800x600 image file supposed to be in PNG ? Actually what I would really like is a table that shows resolutions on the y-axis and formats/compression type on the x-axis. I ask this because I thought I saved an 800x600 72dpi image in PNG and it was 1289 kb which seems kind of big to me.

    Is there a table showing file size like I describe above? I could not find one with search engines.

    • Answers
  • Daniel B

    Anywhere from somewhere around 150 Bytes to somewhere around 1875 Kilobytes. Compression efficiency depends entirely on the contents. An image consisting only of a single solid color being the best case and maximum entropy color (+alpha) noise the worst.

    Reasoning behind these values

    The minimum size is just an estimation (created an image and saved it, now updated with PNGGauntlet). Result was a 152 Byte file.

    The theoretical maximum payload size is 800 * 600 Pixel * 4 Bytes per Pixel (1 Byte per R/G/B + Alpha) = 1,920,000 Bytes. Adding to that are headers and compression overhead.

  • David

    The size of a PNG depends on what the image contains. There is no way to predict the filesize based solely on the dimensions of the image.

    If you want the smallest PNG possible, run your image through PNGGauntlet. It will try several PNG compression tools and then output the one with the smallest filesize.

  • LDC3

    I believe that PNG files are lossless compressed files of the image. So it is very difficult to predict the size of the file since we don't know how the colors are arranged on the image. In fact, the PNG file could even be larger that the raw image data itself.


    • Related Question

    compression - How to compress a huge amount of PNG images?
  • Travis

    At work, on certain projects I have to manage a lot of images. Most of the time PNG files work the best for what I'm doing.

    With such a huge amount of images, I've tried using PNG compression with PNG Gauntlet but sometimes the file doesn't really change and sometimes PNG Gauntlet reports it would've made the filesize bigger!

    Am I just maxing out the compression or is there something more I can do?


    • Related Answers
  • Joseph

    PNG compression is a lossless compression. However, a caveat to this is that there will be times when compressing an image will not always yield the results you want (% compression ratio won't be that great). In contrast to lossful compression (like JPG compression), where you will almost always get a filesize reduction (% compression ratio might be higher), but you actually lose image quality.

  • raspi

    Have you tried PNG Crush?

  • Brad Gilbert

    PNG compression works better for images that have large areas of flat color, like cartoons that are colored with simple color fill, as apposed to a painting which has many colors which look similar, but really aren't.

  • liori

    You should check if you PNG files do really need all the features PNG offers. If it doesn't have man colors, maybe you should switch from 24-bit color to a colortable? If you don't use alpha channel, turn it off. This can make them much smaller.

  • porneL

    You can try all of the PNG compressors at once, e.g. ImageOptim for OS X does that, and that's best you can get with lossless PNG alone.

    However, there are lossy operations you can do to make PNG smaller (easier to compress).

    If you have 24 bit PNG with alpha channel, convert it to paletted PNG with 8-bit alpha channel. pngquant does that (sadly both Photoshop and GIMP pretend such combination cannot exist).

  • Cristián Romo

    I recommend PNGOUT - it works very well. I have never had it make a file larger, and have only had it keep the same file size on rare occasions.

    via Coding Horror

  • Shadok

    Your best bet would be to use Optipng, there are links to GUIs projects for it on their homepage if you need one. The way it works is very efficient size-wise, by trying every combination of compression parameters you have a guarantee to find the better one.

    The drawback is that it will consume more cpu than other techniques because it compresses the same image multiple times to find the smallest one, without any assumption.

    The cool factor here is that you can adjust the optimization level to spare CPU time at your convenience (-o level), in that case assumptions will be made but generally you will not gain anything at testing every possibility.

  • Lynda

    I know this is an old post but I came across it looking for a PNG Optimizer of some sort.

    I found this: PngOptimizer it has a nice interface and I ran 61 files at once, it took about 30 seconds. The 61 files were originally 360kb and it compressed them to 300kb.

    Some files it changed the files only 2 or 3 percent of the original others it reduced by 89%!

    One Note: I never saw it make a larger file. It would say File 100% og original but never larger =>

    It does vary though. Try it and test it for yourself =>

  • slhck

    Use tinypng.org.

    This thing converted my 3 MB image to a 300 KB one. It's amazing!