300dpi text scan very slow document rendering/displaying
Scanning a text with 300dpi is more than 10x slower than with 150dpi.
The slow part is the document rendering (i.e. displaying the document). For 300dpi, a "red line" is filling the page "line by line". It can be watched.
For 600dpi it is the same.
For 150dpi, the page is rendered "immediately". The read line can barely be seen.
Measured times Document Scanner:
150dpi text: 5s
300dpi text: 64s
600dpi text: 64s
150dpi image: 24s
300dpi image: 214s
Xsane comparison
200dpi gray: 5s
300dpi gray: 6s
The actual scanning by the scanner for 150dpi and 300dpi black/white is fast (about 4s). The scanning is without problem. I think the problem is not directly related to the scanner.
The behavior in my setup is fully reproducible.
Document Scanner: 3.34.1
Scanner: HP LaserJet MFP 1522nf
OS: OpenSUSE 15.1 / KDE 5.12.8
GTK2: 2.24.32
GTK3: 3.22.30
My log files produced by 'simple-scan --debug'
simple-scan_150dpi_text_debug.log
simple-scan_300dpi_text_debug.log