Converting bmp to pdf = pdf file size 2 MB LARGER than bmp

[xerkon]

Hi. I scanned a color document and saved it as a .bmp (24 MB) then used batch convert to go from that to pdf using jpeg compression. It worked great and depending on the quality setting I could end up with a nice looking pdf that was a little over 1 MB. I did the exact same thing with a grayscale bitmap, but no matter what I set the jpeg compression quality at, I end up with a file size 2 MB larger than the original. Just for kicks I tried Ifranview and got the expected 1 MB .pdf instead of the 10 MB .pdf file xnview is giving me. Is this a bug, or am I missing something? For some reason I have the feeling a grayscale bmp has an 8 bit color depth, does that sound right? Maybe xnview is having trouble because of that? Also, I tried this same thing in XnviewMP with the same results.

[cday]

In a quick test (hopefully not too quick ) I am seeing something similar:

Small BMP test files, 24-bit and 8-bit grayscale attached.

Created PDF files with JPEG Q=80 compression file sizes 24-bit 7KB and 8-bit 154KB...