Image size

[wefollow]

Hello,

  After I save for web, image showed  800x800 and 176KB.

But when I opened, it showed 1.83M from Photoshop Image size.

Better ask stupid questions then wondering

Thank you for reading it,

[D Fosse]

That's what jpeg compression does. When a jpeg is re-opened, it is decompressed back to its full native size.

This has nothing to do with resolution. Jpeg is a data compression algorithm. As such, it is incredibly effective, often squeezing a file down to 2-5 % of native size on disk.

But at a price. There's no free lunch. Jpeg compression is destructive, cumulative, and non-reversible. Every time you resave a jpeg, it degrades a little bit.

[wefollow]

Now I know why......won't bother me any more.

Thank you for sharing your knowledge,

Enjoy your days and do our best

[jazz-y]

The file on the disk is stored using one or another compression algorithm. After opening, Photoshop "unpacks" and shows how much the file actually takes up in RAM.

When using a color depth of 8bpc, 1 color is encoded in 8 bit. 8 bit = 1 byte. If we are talking about an RGB image, then each pixel contains three colors, then an image of 800x800 pixels takes 800x800x3 = 1,920,000 bytes in memory. Or 1,920,000/1024 = 1875 kB, or 1875/1024 = 1.831 MB.