format: AVIF is the twenty third format, and its encoder is somebody else's

.github/build-tags

@@ -0,0 +1 @@
+noasm

.github/workflows/ci.yml

@@ -71,7 +71,7 @@ jobs:
         shell: bash
 
       - name: vet
-        run: go vet ./...
+        run: go vet -tags "$(cat .github/build-tags)" ./...
 
       - name: the dependency list has not grown by accident
         # Every dependency is a licence question and a byte stability
@@ -133,6 +133,7 @@ jobs:
             github.com/fyne-io/glfw-js \
             github.com/fyne-io/image \
             github.com/fyne-io/oksvg \
+            github.com/gen2brain/gav1d \
             github.com/go-gl/gl \
             github.com/go-gl/glfw/v3.4/glfw \
             github.com/go-ole/go-ole \
@@ -198,8 +199,8 @@ jobs:
           fi
           echo "dependencies unchanged, $(echo "$expected" | wc -l) modules"
 
-          linked=$(go list -deps -f '{{if .Module}}{{.Module.Path}}{{end}}' ./cmd/tfg | LC_ALL=C sort -u | grep -v '^github.com/donislawdev/TestingFilesGenerator$' | grep .)
-          wanted=$(printf '%s\n' github.com/goccy/go-yaml golang.org/x/text)
+          linked=$(go list -deps -tags "$(cat .github/build-tags)" -f '{{if .Module}}{{.Module.Path}}{{end}}' ./cmd/tfg | LC_ALL=C sort -u | grep -v '^github.com/donislawdev/TestingFilesGenerator$' | grep .)
+          wanted=$(printf '%s\n' github.com/gen2brain/gav1d github.com/goccy/go-yaml golang.org/x/text)
           if [ "$linked" != "$wanted" ]; then
             echo "the command line binary links a different set of modules."
             echo "expected: $wanted"
@@ -210,10 +211,10 @@ jobs:
         shell: bash
 
       - name: test
-        run: go test ./... -count=1
+        run: go test -tags "$(cat .github/build-tags)" ./... -count=1
 
       - name: build the command line binary
-        run: go build ./cmd/tfg
+        run: go build -tags "$(cat .github/build-tags)" ./cmd/tfg
 
       - name: build the window binary
         # The toolkit arrived on 2026-08-05 and this step still passes, which
@@ -247,9 +248,9 @@ jobs:
         run: |
           set -euo pipefail
           if [ "$RUNNER_OS" = "Windows" ]; then
-            go build -ldflags="$(cat .github/gui-ldflags)" ./cmd/tfg-gui
+            go build -tags "$(cat .github/build-tags)" -ldflags="$(cat .github/gui-ldflags)" ./cmd/tfg-gui
           else
-            go build ./cmd/tfg-gui
+            go build -tags "$(cat .github/build-tags)" ./cmd/tfg-gui
           fi
         shell: bash
 
@@ -477,8 +478,8 @@ jobs:
         run: |
           set -euo pipefail
           mkdir -p dist
-          CGO_ENABLED=0 go build -trimpath -o dist/tfg ./cmd/tfg
-          CGO_ENABLED=1 go build -trimpath -o dist/tfg-gui ./cmd/tfg-gui
+          CGO_ENABLED=0 go build -tags "$(cat .github/build-tags)" -trimpath -o dist/tfg ./cmd/tfg
+          CGO_ENABLED=1 go build -tags "$(cat .github/build-tags)" -trimpath -o dist/tfg-gui ./cmd/tfg-gui
           ls -l dist
 
       - name: the document we would publish
@@ -645,7 +646,7 @@ jobs:
         # Race instrumentation costs five to twenty times the wall clock, and
         # this package renders twenty five screens and builds two binaries. The
         # job's own thirty minutes is the ceiling that means something.
-        run: go test ./... -count=1 -race -timeout 25m
+        run: go test -tags "$(cat .github/build-tags)" ./... -count=1 -race -timeout 25m
 
   coverage:
     name: coverage gate
@@ -670,7 +671,7 @@ jobs:
         # under test - which reports 0.0% and makes the gate meaningless.
         # Measured, not assumed.
         run: >
-          go test ./... -count=1 -covermode=atomic
+          go test -tags "$(cat .github/build-tags)" ./... -count=1 -covermode=atomic
           -coverpkg=./internal/...,./cmd/...
           -coverprofile=coverage.out
 
@@ -723,13 +724,27 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y --no-install-recommends \
             p7zip-full ffmpeg poppler-utils inkscape python3-pil
+
+          # The distribution's Pillow cannot open an AVIF - measured on this
+          # runner, PIL.UnidentifiedImageError on a file the structural checker
+          # had just called sound. Installed for the SAME interpreter the oracle
+          # reaches for, then asked whether it can actually read one. No version
+          # is named: the question is what this Pillow can do, not when the
+          # support landed.
+          python -m pip install --break-system-packages --upgrade pillow
+          python - <<'PY'
+          from PIL import Image, features
+          print("pillow", Image.__version__, "avif:", features.check("avif"))
+          if not features.check("avif"):
+              raise SystemExit("this Pillow cannot read AVIF, so the oracle would fail on a good file")
+          PY
         shell: bash
 
       - name: every format past its reference tool
         # -v so that a skip is visible in the log. A tool that failed to install
         # would otherwise turn this job back into the green nothing it exists
         # to replace.
-        run: go test ./internal/guard/ -count=1 -run 'ReferenceTool' -v
+        run: go test -tags "$(cat .github/build-tags)" ./internal/guard/ -count=1 -run 'ReferenceTool' -v
         shell: bash
 
   fuzz:
@@ -770,7 +785,7 @@ jobs:
           set -euo pipefail
           for target in FuzzParseSize FuzzParseRecipe FuzzNameTemplate FuzzCanonicalRecipe; do
             echo "=== $target ==="
-            go test ./internal/guard/ -run "^$" -fuzz "^${target}$" -fuzztime 5m
+            go test -tags "$(cat .github/build-tags)" ./internal/guard/ -run "^$" -fuzz "^${target}$" -fuzztime 5m
           done
         shell: bash
 

.github/workflows/release.yml

@@ -51,7 +51,7 @@ jobs:
         # A release built from a red tree is the one kind of release that
         # cannot be taken back, because the binaries are already on somebody's
         # disk. This is the same command CI runs.
-        run: go test ./... -count=1
+        run: go test -tags "$(cat .github/build-tags)" ./... -count=1
 
       - name: what version the code says
         id: version
@@ -188,7 +188,7 @@ jobs:
             # -trimpath keeps the build machine's directory names out of the
             # binary. On a public release that is a privacy line as much as a
             # reproducibility one.
-            GOOS="$os" GOARCH="$arch" go build -trimpath -o "${work}/${binary}" ./cmd/tfg
+            GOOS="$os" GOARCH="$arch" go build -tags "$(cat .github/build-tags)" -trimpath -o "${work}/${binary}" ./cmd/tfg
 
             # The notices travel with the binary because their licences require
             # it - see THIRD-PARTY-NOTICES.md, which says so itself. The licence
@@ -295,10 +295,10 @@ jobs:
             # release and a local build cannot drift. Without them Windows
             # hangs a black console window behind the program. Windows only:
             # the flag names a Windows subsystem and means nothing elsewhere.
-            go build -trimpath -ldflags="$(cat .github/gui-ldflags)" \
+            go build -tags "$(cat .github/build-tags)" -trimpath -ldflags="$(cat .github/gui-ldflags)" \
               -o "${work}/tfg-gui.exe" ./cmd/tfg-gui
           else
-            go build -trimpath -o "${work}/tfg-gui" ./cmd/tfg-gui
+            go build -tags "$(cat .github/build-tags)" -trimpath -o "${work}/tfg-gui" ./cmd/tfg-gui
           fi
 
           # Same reason as the command line archives: on macOS the ticket has

CHANGELOG.md

@@ -34,6 +34,24 @@ because it turns other people's test suites red.
 
 ### Added
 
+- **AVIF, the twenty third format.** One frame, 8 bit, 4:2:0.
+  `tfg generate --format avif --size 300kb` writes an AV1 picture in an ISO base
+  media container. `width`, `height` and `quality` can be set, and the picture
+  goes up to 40 megapixels, so Full HD and 4K are both in reach. Left alone, the
+  picture is the largest of a fixed set that fits the size asked for, up to
+  640x480 - the same as JPG.
+
+  **Every size from its minimum of 311 B upwards is reachable, with no gaps.**
+  The padding travels in a `free` box, which is the box the format sets aside
+  for space that means nothing, and it takes any length at all.
+
+  This is the first format here whose pixels are coded by somebody else's
+  encoder rather than by code in this repository. AV1 is too large to write by
+  hand for one format - the coefficient tables alone in the nearest
+  implementation are fourteen times the size of this project's whole WebP
+  encoder. The encoder is pinned, so raising it is a breaking change like any
+  other, and it is pure Go: no C compiler, no shared library and no socket.
+
 - **WEBP, the twenty second format.** Lossless, one frame, no alpha.
   `tfg generate --format webp --size 300kb` writes a picture worth 300 kB rather
   than a thumbnail followed by filler, because the encoder measures out three

README.md

@@ -10,7 +10,7 @@
 
 **Testing Files Generator** is a tool for QA engineers and developers who need real
 files to test against - an upload form, a parser, anything that takes a file and
-has an opinion about it. You pick one of its 22 formats and the size you want,
+has an opinion about it. You pick one of its 23 formats and the size you want,
 and you get **exactly that**: ask for a 10 MB PDF and you get a PDF that a reader
 will open, at 10 MB to the byte. Every run also leaves a manifest saying **what
 your system should do with each file**, which is the part other generators leave
@@ -23,7 +23,7 @@ needs it finds out it exists.
 
 - **Hit an exact size, to the byte** - ask for 10485761 bytes and get exactly
   that, never a silently rounded file.
-- **Write 22 real formats** - a generated PNG opens in an image viewer, a DOCX
+- **Write 23 real formats** - a generated PNG opens in an image viewer, a DOCX
   opens in Word, a ZIP extracts. Not padded zeros with an extension.
 - **Say what should happen to each file** - the manifest carries an expected
   outcome, so your test reads the assertion instead of you writing it out.
@@ -82,7 +82,7 @@ software that owns it, at the exact size you asked for:
 | group | formats |
 |---|---|
 | 📄 **Documents** | `pdf`, `docx` (Word), `xlsx` (Excel), `pptx` (PowerPoint) |
-| 🖼️ **Images** | `png`, `jpg`, `bmp`, `gif`, `ico`, `svg`, `tiff`, `webp` |
+| 🖼️ **Images** | `png`, `jpg`, `bmp`, `gif`, `ico`, `svg`, `tiff`, `webp`, `avif` |
 | 📝 **Text and markup** | `txt`, `md`, `csv`, `json`, `xml`, `html`, `log` |
 | 🗜️ **Archives** | `zip`, `targz` (`.tar.gz`) |
 | 🔊 **Audio** | `wav` |

THIRD-PARTY-NOTICES.md

@@ -17,14 +17,14 @@ first, so the difference is worth stating rather than leaving to be assumed.
 
 | binary | what it is | third party code in it |
 |---|---|---|
-| `tfg` | the command line | the Go runtime, and **two** modules: `github.com/goccy/go-yaml` and `golang.org/x/text` |
+| `tfg` | the command line | the Go runtime, and **three** modules: `github.com/goccy/go-yaml`, `github.com/gen2brain/gav1d` and `golang.org/x/text` |
 | `tfg-gui` | the desktop window | the same, plus **27** more for the graphics toolkit, one of them on Linux only |
 
 The window is a separate binary because its toolkit needs a C compiler and
 OpenGL, neither of which the command line uses. A server or a build agent
 running `tfg` therefore carries none of the 27, and that is checked rather than
 asserted: a guard in the source compares what the command line binary actually
-links against that list of two.
+links against that list of three.
 
 ---
 
@@ -117,6 +117,48 @@ Source: <https://go.googlesource.com/text>
 
 ---
 
+## github.com/gen2brain/gav1d
+
+Version 0.2.5. Codes and reads AV1, which is what the picture inside an
+AVIF is. It is written in Go and assembly with no C in it and no module
+of its own behind it, so it brings nothing else along.
+
+```
+Copyright (c) 2018-2025, VideoLAN and dav1d authors
+Copyright (c) 2016, Alliance for Open Media
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+```
+
+It also ships a `PATENTS` file carrying the **Alliance for Open Media
+Patent License 1.0**, which grants a patent licence for AV1 and withdraws
+it from anybody who sues over the codec. The full text is in the module,
+at `PATENTS`, and at <https://aomedia.org/license/patent-license/>.
+
+Source: <https://github.com/gen2brain/gav1d>
+
+---
+
 ## The window binary only
 
 These 26 modules are the graphics toolkit and what it brings with it. They are

go.mod

@@ -32,7 +32,10 @@ toolchain go1.26.7
 
 require github.com/goccy/go-yaml v1.19.2
 
-require golang.org/x/text v0.41.0
+require (
+	github.com/gen2brain/gav1d v0.2.5
+	golang.org/x/text v0.41.0
+)
 
 require github.com/FyshOS/fancyfs v0.0.1 // indirect
 
@@ -66,7 +69,7 @@ require (
 	github.com/srwiley/rasterx v0.0.0-20220730225603-2ab79fcdd4ef // indirect
 	github.com/stretchr/testify v1.11.1 // indirect
 	github.com/yuin/goldmark v1.8.2 // indirect
-	golang.org/x/image v0.43.0 // indirect
+	golang.org/x/image v0.43.0
 	golang.org/x/net v0.57.0 // indirect
 	golang.org/x/sys v0.47.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect

go.sum

@@ -22,6 +22,8 @@ github.com/fyne-io/image v0.1.1 h1:WH0z4H7qfvNUw5l4p3bC1q70sa5+YWVt6HCj7y4VNyA=
 github.com/fyne-io/image v0.1.1/go.mod h1:xrfYBh6yspc+KjkgdZU/ifUC9sPA5Iv7WYUBzQKK7JM=
 github.com/fyne-io/oksvg v0.2.0 h1:mxcGU2dx6nwjJsSA9PCYZDuoAcsZ/OuJlvg/Q9Njfo8=
 github.com/fyne-io/oksvg v0.2.0/go.mod h1:dJ9oEkPiWhnTFNCmRgEze+YNprJF7YRbpjgpWS4kzoI=
+github.com/gen2brain/gav1d v0.2.5 h1:Zg5/DE1JBdf8kxZqIvNo2ZEizF9DVF9jdPTAKJQZbOY=
+github.com/gen2brain/gav1d v0.2.5/go.mod h1:ReFKjHq7pvRhEk+pgRPAo9gOlcrf51sdzVcAbbX7e0E=
 github.com/go-gl/gl v0.0.0-20260331235117-4566fea9a276 h1:IO5P06Pcj9K04d+l4nrf3c2U56+dAotIFG6u4P1wAHI=
 github.com/go-gl/gl v0.0.0-20260331235117-4566fea9a276/go.mod h1:9YTyiznxEY1fVinfM7RvRcjRHbw2xLBJ3AAGIT0I4Nw=
 github.com/go-gl/glfw/v3.4/glfw v0.1.0-pre.1.0.20260707082822-2a407d02d01a h1:HWK0MBggT/T6YH7VffE10xBIhqeTq8JzIUPJXrRy87g=

internal/format/all/all.go

@@ -8,6 +8,7 @@ package all
 
 import (
 	// Each format registers itself when its package is loaded.
+	_ "github.com/donislawdev/TestingFilesGenerator/internal/format/avif"
 	_ "github.com/donislawdev/TestingFilesGenerator/internal/format/bmp"
 	_ "github.com/donislawdev/TestingFilesGenerator/internal/format/csvfile"
 	_ "github.com/donislawdev/TestingFilesGenerator/internal/format/docx"