It's very possible that for the purposes of efficiency, Photoshop allocates enough memory so that it can work on the file as though it were in 24 bit color mode. It may be that some filters do a temporary shift to 24 bit color to do their magic, then back to 8 bit. This is just a guess though.
On our copiers, we have the option of scanning to Compact PDF. All it does is use the highest compression for the embedded JPEG images. The copier will not allow the selection of Compact PDF if the color depth is set to grayscale or black and white. Hence, I believe you are correct in your
If your image was 256 colors, the Index > Mode menu would show Indexed Color checked, instead of RGB Color. The RGB/8 Bit you’re seeing in the Photoshop menu actually reads “8 Bits/Channel” — an RGB image is 3 channels (red, green, blue), 8 bits each, so 24 bit color. Again, if you really
Scott is right: JPEG has exactly one _color_ mode: 16M = 2^24 (seen apart of 256 gray-color mode). What you interpret as "8bit-color-mode" relates to the _compression_ mode which also explains the relation filesize vs (uncompressed) size in memory. ___
@ Scott: That's not what I get if I open this image in Photoshop. (CC 2017) 575 X 1000 http://wiki.hindu.org/uploads/img37.jpg It is a JPEG, but under the mode menu it shows "RGB/8 Bit" and if I look under indexed colors it says "256" definitely not 16bit (in which case we should see
You say the mode is 8 bit. I might be wrong, but I don’t believe JPEG supports 8 bit (256 color) images. Even if it does technically, the format is not really intended for 8 bit images, but rather 16 bit or higher. When I generate an 8 bit indexed color image in Photoshop and look at the Save
I think I can answer the Photoshop question. It seems that 1.6 Mb size is the file size for PS to do its work in the application. If you save that file as a .psd, I suspect you’ll see a file size of 1.6 Mb. I find the Save for Web dialog (in the File>Export menu) useful. You can choose the
I'm trying to optimize for Mobile. Photoshop is playing tricks on me given a 38K jpg; rect 3 X 5 552px w 736 px h 72 dpi (irrelevant for screen) Open in Photoshop: it indicates 1.16M in RAM, but mode is 8 bit… but but the online calculation sites for file size for that rect/bit-depth should