I am trying to compress my .jpeg image in Photoshop. WHat is the best way to do this?

I am now calculating the bpp taking the image size in kb, calculating how many bits that is. Then I take the image size in pixel*pixel to get the amount of pixels in the image. After that I divide bits/pixels, to find how many bits per pixel the image has.

But How can I change this number? My guess is to change how many kb the image is, but how do i do this?

Thanks for any help!!

  • 4bpp is not a compression rate, it is a pixel format. Jpeg is always 24bpp. – Hans Passant Jan 28 '12 at 14:48
  • @HansPassant JPEG is either 8bpp or 24bpp. 24bpp JPEGs are much more common. – Bobrovsky Jan 28 '12 at 20:40

Yes, you can achieve higher compression ratio than 4 bits per pixel. Images with solid color can have rate as low as 0.13bpp.

In fact 4bpp is quite poor compression — it's same as uncompressed 16-color image or half of 256-color image, which even GIF can manage. JPEG can look decent at 1-2bpp.

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