This program displays an image with libvips and gtk4. This is supposed to be a slightly useful image viewer. It can display huge (many, many GB) images quickly and without using much memory. It supports many scientific and technical image formats, including TIFF, WEBP, JP2K, JXL, AVIF, HEIC, PNG, JPEG, SVS, MRXS, OpenEXR, GIF, PDF, SVG, FITS, Matlab, NIfTI, Analyze, etc. It supports pixel types from 1 bit mono to 128-bit double precision complex.

All of the UI can make finding the details of image display in the sourcecode difficult. See vipsdisp-tiny for a minimal example --- that's a libvips image viewer in about 300 lines of very commented C.

It all works, though see the TODO list below.

https://youtu.be/KSoBkO2_HtE

This program is on flathub, see:

https://flathub.org/apps/org.libvips.vipsdisp

Just click "install", or enter:

flatpak install flathub org.libvips.vipsdisp

• It supports many scientific and technical image formats, including TIFF, WEBP, JP2K, JXL, HEIC, AVIF, PNG, JPEG, SVS, MRXS, OpenEXR, GIF, PDF, SVG, FITS, Matlab, NIfTI, Analyze, etc. It supports many numeric pixel types, any number of image bands, many colour spaces.

• It doesn't need to keep the whole image in memory. It will only read parts that it needs for display, and it understands most pyramidal image formats. This means you can open and view huge images quickly.

• It has threaded, asynchronous display repaint, so pixels are computed in the background by a pool of workers. The interface stays live even under very heavy load.

• It keeps a sparse pyramid of computed tiles as textures on the GPU. Each frame, it computes the set of visible tiles, and then the GPU scales, positions and composites just those tiles to the screen. CPU load should be low (except for the background workers heh). Hold down i (for "in") or + to do a smooth zoom on the cursor. If you press "d" it toggles a debug display mode which shows the tiles being computed.

• Select Display control bar from the top-right menu and a useful set of visualization options appear. It supports four main display modes: Toilet roll (sorry), Multipage, Animated, and Pages as Bands.

• In Toilet roll mode, a multi-page image is presented as a tall, thin strip of images. In Multipage, you see a single page at a time, with a page-select spinner (you can also use the crtl-< and ctrl-> keys to flip pages). In animated mode, pages flip automatically on a timeout. In pages-as-bands mode, many-page single-band images (eg. OME-TIFF) are presented as a single colour image.

• You can select falsecolour and log-scale filters, useful for many scientific images. Scale and offset sliders let you adjust image brightness to see into darker areas (useful for HDR and many scientific images).

• Select Save as to write an image. It can write most common formats, and lets you set file save options. It can write things like DeepZoom pyramids, PFM, OpenEXR, and so on.

• Select Properties (alt-Enter) to see image metadata. It can display large amounts of metadata (useful for eg. DICOM) with filtering.

• Use alt-Left and alt-Right to move between the set of images being displayed, handy for browsing a directory of images. If you drag or load a set of images, it'll flip between the images in the set. If you drag or load a single image, it'll flip between all the images in that directory.

• It keeps the most recent three views live, so you can flip between them very quickly, and all view settings are preserved. This is handy for comparing details on two images.

• Duplicate window crtl-D makes a copy of the window, so you can compare two images side by side.

• It supports copy/paste and drag/drop of filenames, sets of filenames, and textures. You can paste from the screenshot tool, or drag-drop images from your file browser, for example.

• It uses the gtk4 GUI toolkit, so the interface is fast, attractive and nicely animated. The image is rendered with the GPU, so display ought to be quick.

• Cursor keys to scroll around
• Cursor keys plus shift to move by a screen size
• Cursor keys plus ctrl to move to image edges
• Number keys to pick a particular magnification
• Ctrl + number keys to pick a particular zoom out
• 0 for best fit
• d, to toggle debug rendering mode
• i, + / o, - to zoom in and out
• ctrl-< / ctrl->. prev page, next page
• alt-Left / alt-Right. prev image, next image
• Mouse drag to pan
• Mousewheel to zoom
• Mousewheel + shift/ctrl to pan
• ^O replace image
• ^S save image
• ^N new viewer
• ^D duplicate view
• alt-Enter toggle properties
• ^C / ^V copy paste of filenames, lists of filenames and textures
• F11 fullscreen

Additionally, you can drag and drop filenames, lists of filenames and textures.

cd vipsdisp
meson setup build --prefix=~/vips
cd build
ninja
ninja install

And to run:

export GSETTINGS_SCHEMA_DIR=/home/john/vips/share/glib-2.0/schemas
vipsdisp ~/pics/k2.jpg

Version needs updating in the following places:

• CHANGELOG.md

• meson.build

• org.libvips.vipsdisp.metainfo.xml and some release notes and a date as well. Be exttremely careful with date formatting, and include leading zeros on the day and month.

• org.libvips.vipsdisp.json needs the version number as a git tag.

Add the flathub repo:

flatpak remote-add --if-not-exists \
  flathub https://flathub.org/repo/flathub.flatpakrepo

Install the gtk4 SDK and runtime:

flatpak install org.gnome.Sdk//45
flatpak install org.gnome.Platform//45

Allow file. Recent security changes to git will cause submodule checkout to fail inside flatpak. If you get errors like fatal: transport 'file' not allowed, re-enable file transport with:

git config --global protocol.file.allow always

Build and try running it:

flatpak-builder --force-clean --user --install build-dir org.libvips.vipsdisp.json
flatpak run org.libvips.vipsdisp ~/pics/k2.jpg

Force a complete redownload and rebuild (should only rarely be necessary) with:

rm -rf .flatpak-builder

Check the files that are in the flatpak you built with:

ls build-dir/files

Uninstall with:

flatpak uninstall vipsdisp

• niftiio is annoying to build, skip it.

• x265 is annoying to build, skip it

• we skip imagemagick as well, too huge

Install the appdata checker:

flatpak install flathub org.freedesktop.appstream-glib
flatpak run org.freedesktop.appstream-glib validate org.libvips.vipsdisp.metainfo.xml

Also:

desktop-file-validate org.libvips.vipsdisp.desktop 

Make a PR on:

    https://github.com/flathub/org.libvips.vipsdisp 

then check the build status here:

    https://flathub.org/builds/#/apps/org.libvips.vipsdisp

On success, merge to master.

• PDF page change does not change image size if pages vary in size

• ^C during a slow load leaves a file in /tmp, can we improve this?

• batch save?

• pass revalidate down to new_from_file on F5

• have a look at the new 4.14 gtk_print_dialog_new()

  works and is in branch add-print-dialog, but it needs 4.14, and the new print API is still unstable

• allow eg. "vipsdisp x.svg[scale=10]", the load dialog should have a "load options" expander

• can we move new_from_file into a bg thread? the GUI will pause on huge SVGs on zoom change right now

  very difficult with the current structure -- we'd need to separate tilesource and tilecache completely, and perhaps link them with signals

• tile read errors:

  $ ./src/vipsdisp ~/pics/ome/LuCa-7color_Scan1.ome.tiff

    - (vipsdisp:110067): VIPS-WARNING **: 18:05:16.244: 
        error in tile 0 x 256: tiff2vips: 
            out of order read -- at line 3328, but line 256 requested
  

  page 0, subifd 2 and subifd 3 are untiled!!!

  we need to decompress the whole layer before we view :(

• need to separate page and zoom for ome-tiff, since we have many-page subifd pyramids

  • useful for fixing PDF zoom in the way we fixed SVG zoom too

• pages as bands

  $ ./src/vipsdisp ~/pics/ome/LuCa-7color_Scan1.ome.tiff

    flip to last page, zoom, lots of repaint errors
  
    maybe join first N pages (while pages same size) in pages as bands 
    mode?
  
    does not page flip to smaller pages correctly
  
        reset zoom/scroll on pageflip if the page size changes?
  
    same for audi r8 pdf page flip I guess?
  

• info bar:

  • pages as bands ... info bar displays only one band

  • will not display complex numbers correctly ... need to unpack to bands, or does getpoint do this already?

• zooming:

  • better pinch zoom support

    we should take the coordinates of the pinch gesture into account

    can test this now I have a multitouch trackpad

  • we could shrink tiles on zoom out (we only expand tiles now)

  • before we can do fancy PDF zooming, we'll need to split page and zoom in tile_source_open()

• how should we handle images which include labels, macros, thumbnails?

  • load options? save options?

  • display images in properties? perhaps a thumbnail? set attach-associated?

    appear as eg.:

    openslide.associated.thumbnail 1024x732 uchar, 4 bands, srgb