Rewritten completely: fullscreen widget instead of mainwindow. Just viewing image for now. Added some usage message and reading filename from command line.
Added zooming.
Added canvas moving (shifting), canvas centering (returning it to the center. Added Q key for exiting.
Added cursor and controlling of it. Added option to show explicit cursor position.
Added small rect area for displaying color under cursor.
Added picking color under cursor and putting current color at the current pos. Made it aware of 1, 8 (paletted) and 32 bit (truecolor) images.
Added palette detection and displaying palette for non-TrueColor images.
Added option to change current color using # key. Takes palette into consideration.
Added option to pick color by scrolling through palette.
Made a proper README.