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.
33 Answers
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 valuesThe 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.
5The 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.
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.
