85 lines
3 KiB
Nix
85 lines
3 KiB
Nix
import ./make-test-python.nix ({ pkgs, ... }:
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/*
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SANE NixOS test
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===============
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SANE is intrisically tied to hardware, so testing it is not straightforward.
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However:
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- a fake webcam can be created with v4l2loopback
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- sane has a backend (v4l) to use a webcam as a scanner
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This test creates a webcam /dev/video0, streams a still image with some text
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through this webcam, uses SANE to scan from the webcam, and uses OCR to check
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that the expected text was scanned.
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*/
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let
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text = "66263666188646651519653683416";
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fontsConf = pkgs.makeFontsConf {
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fontDirectories = [
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pkgs.dejavu_fonts.minimal
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];
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};
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# an image with black on white text spelling "${text}"
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# for some reason, the test fails if it's jpg instead of png
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# the font is quite large to make OCR easier
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image = pkgs.runCommand "image.png"
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{
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# only imagemagickBig can render text
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nativeBuildInputs = [ pkgs.imagemagickBig ];
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FONTCONFIG_FILE = fontsConf;
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} ''
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magick -pointsize 100 label:${text} $out
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'';
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in
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{
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name = "sane";
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nodes.machine = { pkgs, config, ... }: {
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boot = {
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# create /dev/video0 as a fake webcam whose content is filled by ffmpeg
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extraModprobeConfig = ''
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options v4l2loopback devices=1 max_buffers=2 exclusive_caps=1 card_label=VirtualCam
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'';
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kernelModules = [ "v4l2loopback" ];
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extraModulePackages = [ config.boot.kernelPackages.v4l2loopback ];
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};
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systemd.services.fake-webcam = {
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wantedBy = [ "multi-user.target" ];
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description = "fill /dev/video0 with ${image}";
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/* HACK: /dev/video0 is a v4l2 only device, it misses one single v4l1
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ioctl, VIDIOCSPICT. But sane only supports v4l1, so it will log that this
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ioctl failed, and assume that the pixel format is Y8 (gray). So we tell
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ffmpeg to produce this pixel format.
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*/
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serviceConfig.ExecStart = [ "${pkgs.ffmpeg}/bin/ffmpeg -framerate 30 -re -stream_loop -1 -i ${image} -f v4l2 -pix_fmt gray /dev/video0" ];
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};
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hardware.sane.enable = true;
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system.extraDependencies = [ image ];
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environment.systemPackages = [
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pkgs.fswebcam
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pkgs.tesseract
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pkgs.v4l-utils
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];
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environment.variables.SANE_DEBUG_V4L = "128";
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};
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testScript = ''
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start_all()
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machine.wait_for_unit("fake-webcam.service")
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# the device only appears when ffmpeg starts producing frames
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machine.wait_until_succeeds("scanimage -L | grep /dev/video0")
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machine.succeed("scanimage -L >&2")
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with subtest("debugging: /dev/video0 works"):
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machine.succeed("v4l2-ctl --all >&2")
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machine.succeed("fswebcam --no-banner /tmp/webcam.jpg")
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machine.copy_from_vm("/tmp/webcam.jpg", "webcam")
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# scan with the webcam
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machine.succeed("scanimage -o /tmp/scan.png >&2")
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machine.copy_from_vm("/tmp/scan.png", "scan")
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# the image should contain "${text}"
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output = machine.succeed("tesseract /tmp/scan.png -")
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print(output)
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assert "${text}" in output, f"expected text ${text} was not found, OCR found {output!r}"
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'';
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})
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