Framebuffer image viewer

Framebuffer resolution

Set the framebuffer resoultion by modifying /boot/config.txt:

# uncomment to force a specific HDMI mode (this will force VGA)
hdmi_group=2
hdmi_mode=87

# See /boot/overlays/README for all available options
hdmi_cvt 3840 2160 15
max_framebuffer_width=3840
max_framebuffer_height=2160

Reboot and check the resolution:

fbset

Install image editor

ImageMagick provides a set of tools to edit bitmap images and Image::Magick a Perl interface to it.

Install it:

su
apt install imagemagick
apt install libimage-magick-perl

Test it:

find /usr/share/ -iname *.jpg 2> /dev/null
identify /usr/share/pixmaps/debian-logo.png
RESOLUTION='3840x2160'
convert -resize $RESOLUTION -background black -gravity center -extent $RESOLUTION /usr/share/pixmaps/debian-logo.png bgra:/dev/fb0

perl -MImage::Magick -le 'print Image::Magick->QuantumDepth'