rewrite the README

It had drifted out of agreement with itself. The manifest section still said
`image` is std/core/v1/UInt8 and depth and camera_info are std/core/v1/Float32,
four lines above a table correctly saying both are std/media/v1/Image, and the
worked example for a producer showed the flat-buffer form the node moved away
from. Someone following it would have written a producer that fails validate.

It was also close to twice the length of the one next door, mostly rationale:
why a dataflow carries no strict_types, how a producer migrates, what a git:
node needs and why. That belongs in the file it explains or in the commit that
made the decision, not in front of someone trying to wire a node.

1007 words, from 1749. Every encoding, environment variable and CLI flag in it
was checked against the code.

README.md

@@ -1,11 +1,12 @@
 # dora-image-view
 
 Dora node that displays a colour image and a depth map side by side in one OpenCV
-window, with bounding box, text and camera intrinsics overlays. A display sink for debugging a
+window, with bounding box, text and camera intrinsics overlays. A display sink for
-vision pipeline: it produces no outputs.
+debugging a vision pipeline: it consumes frames and produces no outputs.
 
 Based on [`opencv-plot`](https://github.com/dora-rs/dora-hub/tree/main/node-hub/opencv-plot)
-from dora-hub, brought up to the dora 1.0 node contract and packaged with `uv`.
+from dora-hub, brought up to the dora 1.0 node contract, renamed, and changed to take
+the typed Arrow image struct rather than a flat buffer plus metadata.
 
 ## Usage
 
@@ -15,123 +16,44 @@ Add to your dataflow:
 nodes:
   - id: view
     git: https://gitea.liria.cl/liria/dora-image-view.git
-    tag: v0.1.0
+    tag: v0.1.1
     build: uv pip install .
     path: dora-image-view
     inputs:
-      image: camera/image_bgr
+      image: camera/image
       depth: camera/depth
       camera_info: camera/camera_info
       bbox: detector/bbox
       text: detector/text
 ```
 
-Run the dataflow with `--uv` (`dora run dataflow.yml --uv`) so the node gets its own
+Run the dataflow with `--uv` (`dora run dataflow.yml --uv`): the build command is
-managed environment.
+`uv pip install .`, so the node gets its own managed environment and never installs into
+an ambient one.
 
-Every input is optional, and each of `image` and `depth` fills one panel of the window,
+Every input is optional. `image` and `depth` each fill a panel, tiled left to right and
-tiled left to right in that order. Wiring one of them is a plain viewer;
+scaled to a common height, so wiring one is a plain viewer and wiring both shows them
-wiring several shows them side by side, scaled to a common height. `bbox`, `text` and `camera_info`
+side by side. `bbox`, `text` and `camera_info` are overlays rather than panels: boxes on
-are overlays rather than panels — boxes are drawn on the `image` panel, in its own
+the image panel in its own pixels, caption and camera model on the composite.
-pixels, and the caption on the composite.
 
-### End-to-end test
+### Runnable dataflows
 
-[`dataflow.yml`](dataflow.yml) is self-contained. [`tests/source.py`](tests/source.py)
+Run either with `dora run <file> --uv`:
-is a synthetic source node that emits an animated frame, a depth map of the same scene,
-the camera intrinsics, the box around the square moving in the frame, and a caption —
-every input this node draws — so it needs no camera, no detector and no network. It is
-a test fixture rather than a worked example; the realistic wiring is the block at the
-top of this file. Run it to watch the node work:
 
-```bash
+| File | Contents |
-dora run dataflow.yml --uv
+|---|---|
-```
+| [`dataflow.yml`](dataflow.yml) | A synthetic source driving every input. What CI runs. |
+| [`dataflow_webcam.yml`](dataflow_webcam.yml) | A real camera, via [dora-webcam][webcam] |
 
-A window opens with a square bouncing across a gradient, boxed and labelled. Press `q`
+[webcam]: https://gitea.liria.cl/liria/dora-webcam
-to quit.
 
-It builds the viewer from this checkout (`path:` + `build:`) rather than from a tag,
+`dataflow.yml` needs no camera, no detector and no network: a window opens with a square
-which is what lets `dora validate` pick up the manifest described below.
+bouncing across a gradient, boxed and labelled, beside its depth map. Press `q` to quit.
+CI runs it headless on every push, which is what keeps it from rotting.
 
-CI runs the same dataflow headless on every push, which is what makes it a gate rather
+`dataflow_webcam.yml` is the worked example of consuming a real producer. A `git:` node
-than a demo that rots.
+needs **anonymous** read access to fetch — on Gitea that means a public organization, not
-
+just a public repository.
-Set `SOURCE_FRAMES` to stop the source after a fixed number of frames instead of running
-until you quit; that plus `CI=true` is how the same dataflow runs headless as a test:
-
-```bash
-CI=true SOURCE_FRAMES=30 dora run dataflow.yml --uv
-```
-
-`SOURCE_WIDTH` and `SOURCE_HEIGHT` (default 640x480) set the frame size.
-
-### With a real camera
-
-[`dataflow_webcam.yml`](dataflow_webcam.yml) wires
-[dora-webcam](https://gitea.liria.cl/liria/dora-webcam) into this node, and is the
-worked example of consuming something that is not a test fixture:
-
-```bash
-dora run dataflow_webcam.yml --uv
-```
-
-The camera publishes `std/media/v1/Image` and this node draws it. `depth`,
-`camera_info`, `text` and `bbox` are simply unwired — every input is optional, so a
-plain viewer is the result.
-
-It carries no `strict_types`, deliberately. A camera publishes an image and nothing
-else, and `dora validate --strict` warns about every *typed* input this node declares
-that a dataflow leaves unwired. The strictness belongs to `dataflow.yml`, which drives
-all of them.
-
-**A `git:` node needs anonymous read access.** dora-cli 1.0.1 fetches through libgit2
-with no credential callback, so a repository that asks for credentials fails with
-`remote authentication required but no callback set`, and `ssh://` cannot authenticate
-at all. Note that marking a repository public is not sufficient on Gitea: a repository
-inside a **private organization** is treated as internal and still answers anonymous
-clones with `401`. The organization has to be public too.
-
-### Node manifest
-
-[`dora-node.yml`](dora-node.yml) declares the node's inputs with type URNs. No source
-package is shared between node repositories, so it is the only contract a consumer has,
-and it is what makes a wiring mistake fail at build time instead of at runtime. The
-example source is typed inline in the dataflow with `output_types:`, so `dora validate`
-checks the two against each other:
-
-```text
-$ dora validate dataflow.yml
-  node "view": injected 4 contract type(s) from .../dora-node.yml
-All type annotations OK.
-```
-
-There is one manifest because this repository ships one node. The example source is a
-test fixture rather than something anyone installs, so it has none, and runs through
-the interpreter to keep `dora validate` from matching the viewer's manifest against it.
-
-`image` is `std/core/v1/UInt8`, `depth` and `camera_info` are `std/core/v1/Float32` and
-`text` is `std/core/v1/String`; the payloads are raw buffers described by their
-metadata, so the URN names the element type rather than a struct. `bbox` is deliberately
-left untyped — senders disagree on whether its numeric fields are 32- or 64-bit, and the
-node reads either.
-
-## Behavior
-
-The node keeps a current frame, bbox set and text string. Each input updates its slice
-of that state:
-
-- An **`image`** event decodes the frame and immediately redraws: it draws every stored
-  bbox (green rectangle plus `label, conf` text), draws the stored text at the top left,
-  resizes to `VIEW_WIDTH`x`VIEW_HEIGHT` if both are set, and shows it in a window titled
-  `Dora Node: dora-image-view`. Press `q` in the window to quit.
-- A **`depth`** event colour-maps the distances onto the depth panel and redraws.
-- A **`camera_info`** event stores the pinhole model and draws it under the caption.
-- A **`bbox`** or **`text`** event only updates stored state; it is drawn on the next
-  redraw.
-
-Setting `CI=true` suppresses the display: the node still decodes every input but opens
-no window. That is what makes it safe to run in a pipeline test.
 
 ## Inputs
 
@@ -139,59 +61,42 @@ no window. That is what makes it safe to run in a pipeline test.
 |---|---|---|
 | `image` | `std/media/v1/Image` struct | none — the struct describes itself |
 | `depth` | `std/media/v1/Image` struct, one channel | `units` (defaults to `mm`) |
-| `camera_info` | `[fx, fy, cx, cy]` or a 9-element K | `distortion`, `distortion_model` |
+| `camera_info` | `[fx, fy, cx, cy]` or a 9-element row-major `K` | `distortion` |
-| `bbox` | Arrow struct array, element `[0]` with fields `bbox`, `conf`, `labels` | `format` |
+| `bbox` | Arrow struct `{bbox, conf, labels}` | `format`: `xyxy` or `xywh` |
 | `text` | Arrow array of size 1 | — |
 
 `image` and `depth` are both `std/media/v1/Image`: an Arrow struct of `width: UInt32`,
-`height: UInt32`, `encoding: Utf8` and `data: LargeBinary`. The payload describes
+`height: UInt32`, `encoding: Utf8` and `data: LargeBinary`. The payload describes itself,
-itself, so nothing about its shape has to travel as message metadata.
+so nothing about its shape travels as message metadata.
 
-Depth is an image whose pixels are distances — dora's type registry has no depth type,
+Image encodings: `bgr8`, `rgb8`, `yuv420`, `avif`, and `jpeg`/`jpg`/`jpe`/`bmp`/`webp`/
-and this is how ROS spells it too. Its encodings are `32FC1`/`float32` and
+`png` as an encoded byte stream. Depth encodings: `32FC1`/`float32` and
-`16UC1`/`mono16`/`uint16`, one channel per pixel, and `units` metadata still switches
+`16UC1`/`mono16`/`uint16`, one channel per pixel — dora's registry has no depth type, and
-millimetres to metres.
+a depth map is an image whose pixels are distances, as ROS also treats it. `0` and
+non-finite values mean missing depth and draw black.
+
+`camera_info` is also read from the metadata of any frame carrying `fx`, `fy`, `cx` and
+`cy`, so **wiring it is optional even for a camera that publishes it** — which covers a
+camera that publishes it once per session and a viewer started afterwards. The node needs
+none of it to draw; it is held for whatever turns depth into 3D.
 
 Older payloads are still decoded, so a producer can move at its own pace: a flat `UInt8`
-buffer with `width`/`height`/`encoding` metadata for `image`, and a flat `Float32`
+buffer with `width`/`height`/`encoding` metadata for `image`, and a flat `Float32` buffer
-buffer with `shape`/`units` metadata for `depth`.
+with `shape`/`units` for `depth`. Note that dora's type compatibility is directional, so
+a producer still *declaring* `std/core/v1/UInt8` fails `dora validate` against an
+`std/media/v1/Image` input whatever it sends — its manifest has to move too.
 
-**Migrating a producer.** dora's type compatibility is directional — `Image` satisfies a
+Publishing to it:
-`Bytes` input, but a `std/core/v1/UInt8` output wired into an `std/media/v1/Image` input
-is a `dora validate` error. A producer still declaring `std/core/v1/UInt8` or
-`std/core/v1/Float32` therefore has to change its manifest as well as its payload.
-
-Supported `image` `encoding` values: `bgr8`, `rgb8`, `jpeg`/`jpg`/`jpe`/`bmp`/`webp`/`png`
-(encoded byte stream), `yuv420`, `avif`. `width` and `height` are only needed by the raw
-encodings — the rest carry their own dimensions. An unsupported encoding raises.
-
-Supported `format` values: `xyxy` and `xywh` (centre-based, converted to `xyxy`).
-
-`depth` is in millimetres unless `units` is `m`. In a depth map, `0`
-and any non-finite value mean missing depth and are drawn black. A payload sent as a
-raw byte slice — which is what a C++ node does — arrives as `UInt8` despite the
-`Float32` contract, and is reinterpreted rather than converted.
-
-### Camera intrinsics
-
-`camera_info` carries the pinhole model the depth map is interpreted through, either as
-the four values `[fx, fy, cx, cy]` or as a nine-element row-major `K`, which is how ROS
-spells the same model in `sensor_msgs/CameraInfo`. Distortion coefficients are read from
-the `distortion` metadata.
-
-The node displays the model and holds it. It needs none of it to draw a panel; it is
-there for what reads it next — turning a depth map into a point cloud needs `fx`, `fy`,
-`cx` and `cy` for every pixel, and nothing else in a dataflow carries them.
-
-Intrinsics are also picked up from the metadata of any `image` or `depth` frame that
-carries `fx`, `fy`, `cx` and `cy`, so **wiring `camera_info` is optional even for a
-camera that publishes it**. That matters because a camera typically publishes
-`camera_info` once per session: a viewer started after the camera would otherwise never
-see it.
 
 ```python
-node.send_output("image", pa.array(frame.ravel()),
+image = pa.array(
-                 {"width": 640, "height": 480, "encoding": "bgr8"})
+    [{"width": 640, "height": 480, "encoding": "bgr8", "data": frame.tobytes()}],
+    type=pa.struct([
+        ("width", pa.uint32()), ("height", pa.uint32()),
+        ("encoding", pa.utf8()), ("data", pa.large_binary()),
+    ]),
+)
+node.send_output("image", image, {})
 
 node.send_output("bbox", pa.array([{
     "bbox": np.array([...]),    # flattened, four values per box
@@ -206,7 +111,19 @@ node.send_output("text", pa.array(["hello"]))
 
 None — it is a display sink.
 
-## Environment variables
+## Configuration
+
+Settings are environment variables, which a dataflow can carry per node, keeping them
+with the wiring rather than in whatever shell starts it:
+
+```yaml
+    env:
+      VIEW_DEPTH_MIN_MM: 200
+      VIEW_DEPTH_MAX_MM: 600
+```
+
+A node's `env:` wins over the environment the dataflow was started in; variables it does
+not set still pass through.
 
 | Variable | Default | Meaning |
 |---|---|---|
@@ -215,18 +132,16 @@ None — it is a display sink.
 | `VIEW_DEPTH_MIN_MM` | auto | Pin the near end of the depth colour range, in millimetres. |
 | `VIEW_DEPTH_MAX_MM` | auto | Pin the far end of the depth colour range, in millimetres. |
 
-Resizing only happens when both `VIEW_WIDTH` and `VIEW_HEIGHT` are set. Both are also
+Resizing only happens when both `VIEW_WIDTH` and `VIEW_HEIGHT` are set; both are also
-available as `--view-width` and `--view-height`; the environment variable wins when both
+available as `--view-width` and `--view-height`, and the environment variable wins.
-are given.
 
-Each end of the depth range is auto-ranged over the valid pixels of the current frame
+Each end of the depth range is auto-ranged over the current frame's valid pixels unless
-unless it is pinned, so pinning one end leaves the other automatic. Auto-ranging makes
+pinned, so pinning one end leaves the other automatic. Auto-ranging makes an
-an unconfigured sensor legible at the cost of colours that shift from frame to frame;
+unconfigured sensor legible at the cost of colours that shift between frames; pin both
-pin both ends to compare frames against each other. The range covers the full extent of
+ends to compare frames against each other.
-the valid pixels rather than a percentile of them, so a small near object against a
-large wall stays visible.
 
-`CI=true` suppresses the display window; it is not a configuration knob.
+`CI=true` suppresses the window while still decoding every input, which is what makes the
+node safe inside a pipeline test. It is not a configuration knob.
 
 ## Build
 
@@ -235,13 +150,12 @@ uv sync
 ```
 
 Every dependency ships prebuilt wheels for linux-x86_64, linux-aarch64 and macos-arm64,
-so the node installs with no system packages and no compiler on any of them — including
+so the node installs with no system packages and no compiler — including AVIF support,
-AVIF support, which comes from `pillow-avif-plugin` rather than OpenCV.
+which comes from `pillow-avif-plugin` rather than OpenCV.
 
 **Requirements:** dora 1.0+ (verified with `dora-cli 1.0.1`), Python 3.11+, `uv`, and a
-display to show the window on (or `CI=true` to run without one). On a bare Linux image
+display (or `CI=true` to run without one). On a bare Linux image `opencv-python` needs
-`opencv-python` also needs the libGL shared libraries (`libgl1`, `libglib2.0-0`), which
+the libGL shared libraries (`libgl1`, `libglib2.0-0`), which it links at import time.
-it links at import time.
 
 ## Test
 
@@ -249,6 +163,6 @@ it links at import time.
 uv run pytest
 ```
 
-Unit tests over decoding, the bbox format conversion and the headless draw path; they
+Unit tests over decoding, depth, intrinsics, the bbox conversion and the headless draw
-need neither a camera, a dataflow nor a display. The headless dataflow run above covers
+path; they need neither a camera, a dataflow nor a display. The headless `dataflow.yml`
-the rest — the manifest, the wiring and the event loop.
+run covers the rest — the manifest, the wiring and the event loop.

dataflow_webcam.yml

@@ -5,10 +5,11 @@
 # dataflow.yml is the gate, and needs neither.
 #
 # This needs anonymous read access to the camera's repository. dora-cli 1.0.1
-# fetches through libgit2 with no credential callback, so anything that asks for
+# fetches through libgit2 with no credential callback, so ssh:// cannot
-# credentials fails with "remote authentication required but no callback set".
+# authenticate at all and anything asking for credentials fails with "remote
-# On Gitea, marking the repository public is not enough: a repository inside a
+# authentication required but no callback set". On Gitea, marking the repository
-# private organization is internal and still answers anonymous clones with 401.
+# public is not enough: a repository inside a private organization is internal
+# and answers an anonymous clone with 401, so the organization must be public.
 #
 # `strict_types` is deliberately absent. A camera publishes an image and nothing
 # else, and `dora validate --strict` warns about every *typed* input this node
@@ -19,7 +20,7 @@
 nodes:
   - id: camera
     git: https://gitea.liria.cl/liria/dora-webcam.git
-    tag: v0.1.0
+    tag: v0.1.1
     build: uv pip install .
     path: dora-webcam
     inputs:

pyproject.toml

@@ -37,6 +37,13 @@ build-backend = "hatchling.build"
 [tool.hatch.build.targets.wheel]
 packages = ["dora_image_view"]
 
+[tool.pytest.ini_options]
+# Only this repository's tests. `dora run` vendors a `git:` node's source into
+# git/ inside the checkout, and pytest would otherwise collect that node's tests
+# too -- reporting another project's results as this one's, and going red when
+# they fail.
+testpaths = ["tests"]
+
 [tool.ruff.lint]
 extend-select = ["D", "I", "N", "RET", "UP"]