There are plenty of very capable image viewers around, but for very large images (several hundred megapixels to a few gigapixels), most start to struggle. GPix is a viewer that can readily handle grayscale images up to a few gigapixels on contemporary hardware.
GPix requires opencv version 3.0 or later and Qt version 5.5 or later. In Debian-style Linuxes, these may be installed by typing:
sudo apt install libopencv-dev qtbase5-dev
To build from source in Linux, simply type
make
followed by
sudo make install
To build from source in Windows or Mac, please load “src/gpix.pro” in Qt Creator and compile from there.
To run on an 8-bit grayscale image, type
gpix <imagefile>
or just
gpix
to open a dialog to select the image.
GPix can also handle 16-bit grayscale images. In that case, “contrast stretching” is usually recommended. To clip 0.5% of pixels on the black side of the histogram and 0.2% of pixels on the white side, type
gpix -b 0.5 -w 0.2 <imagefile>
For complete information on command-line use, type
gpix --help
GPix currently converts color images to grayscale.
GPix works by loading the image file, than precalculating reduced-size versions of the image by successively averaging over 2x2-pixel areas. This allows it to zoom and pan around large images much more quickly than other programs.
When gpix starts, it zooms out to show the entire image in its window. Press “+” to zoom in and “-” to zoom out. Press “/” to enable a navigator inset that indicates what part of the full image is being shown. Press “*” to open a panel with adjustment sliders for black level, white level, gamma adjustment, and low-pass filtering.
Drag the mouse to slowly move around the image, use the scroll wheel to move more rapidly around the image. Control + scroll zooms in and out.
GPix is very new. Your thoughts for features are very welcome.