C++ examples & roundtrip tests for image/segmentation-image/depth-ima…

…ge/tensor (#3899)

### What

* Fixes #3380
* Part of #2919

commit history is a bit messy because this was based on the annotation
context example pr. Speaking off, I made those a bit nicer on the way


### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/3899) (if
applicable)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG

- [PR Build Summary](https://build.rerun.io/pr/3899)
- [Docs
preview](https://rerun.io/preview/c324163602dfdde33684cae0f9365fd72b177ad3/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/c324163602dfdde33684cae0f9365fd72b177ad3/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://ref.rerun.io/dev/bench/)
- [Wasm size tracking](https://ref.rerun.io/dev/sizes/)

crates/re_types/definitions/rerun/archetypes/depth_image.fbs

@@ -14,7 +14,8 @@ namespace rerun.archetypes;
 /// \example depth_image_simple !api title="Simple example" image="https://static.rerun.io/depth_image_simple/9598554977873ace2577bddd79184ac120ceb0b0/1200w.png"
 /// \example depth_image_3d title="Depth to 3D example" image="https://static.rerun.io/depth_image_3d/f78674bdae0eb25786c6173307693c5338f38b87/1200w.png"
 table DepthImage (
-  "attr.rust.derive": "PartialEq"
+  "attr.rust.derive": "PartialEq",
+  "attr.cpp.no_field_ctors"
 ) {
   // --- Required ---
 

crates/re_types/definitions/rerun/archetypes/image.fbs

@@ -18,7 +18,8 @@ namespace rerun.archetypes;
 ///
 /// \example image_simple image="https://static.rerun.io/image_simple/06ba7f8582acc1ffb42a7fd0006fad7816f3e4e4/1200w.png"
 table Image (
-  "attr.rust.derive": "PartialEq"
+  "attr.rust.derive": "PartialEq",
+  "attr.cpp.no_field_ctors"
 ) {
   // --- Required ---
 

crates/re_types/src/archetypes/image_ext.rs

@@ -28,7 +28,7 @@ impl Image {
                 assign_if_none(&mut data.shape[non_empty_dim_inds[1]].name, "width");
             }
             3 => match data.shape[non_empty_dim_inds[2]].size {
-                3 | 4 => {
+                1 | 3 | 4 => {
                     assign_if_none(&mut data.shape[non_empty_dim_inds[0]].name, "height");
                     assign_if_none(&mut data.shape[non_empty_dim_inds[1]].name, "width");
                     assign_if_none(&mut data.shape[non_empty_dim_inds[2]].name, "depth");

crates/re_types/src/archetypes/tensor_ext.rs

@@ -24,7 +24,7 @@ impl Tensor {
     ///
     /// If too many, or too few names are provided, this function will warn and only
     /// update the subset of names that it can.
-    pub fn with_names(self, names: impl IntoIterator<Item = impl Into<ArrowString>>) -> Self {
+    pub fn with_dim_names(self, names: impl IntoIterator<Item = impl Into<ArrowString>>) -> Self {
         let names: Vec<_> = names.into_iter().map(|x| Some(x.into())).collect();
         if names.len() != self.data.0.shape.len() {
             re_log::warn_once!(

docs/code-examples/annotation_context_segmentation.cpp

@@ -2,6 +2,8 @@
 
 #include <rerun.hpp>
 
+#include <algorithm>
+
 int main() {
     auto rec = rerun::RecordingStream("rerun_example_annotation_context_connections");
     rec.connect("127.0.0.1:9876").throw_on_failure();
@@ -19,17 +21,12 @@ int main() {
     const int HEIGHT = 8;
     const int WIDTH = 12;
     std::vector<uint8_t> data(WIDTH * HEIGHT, 0);
-    for (auto y = 0; y < 4; ++y) { // top half
-        auto row = data.begin() + y * WIDTH;
-        std::fill(row, row + 6, 1); // left half
+    for (auto y = 0; y < 4; ++y) {                   // top half
+        std::fill_n(data.begin() + y * WIDTH, 6, 1); // left half
     }
-    for (auto y = 4; y < 8; ++y) { // bottom half
-        auto row = data.begin() + y * WIDTH;
-        std::fill(row + 6, row + 12, 2); // right half
+    for (auto y = 4; y < 8; ++y) {                       // bottom half
+        std::fill_n(data.begin() + y * WIDTH + 6, 6, 2); // right half
     }
 
-    rec.log(
-        "segmentation/image",
-        rerun::SegmentationImage(rerun::TensorData({HEIGHT, WIDTH}, std::move(data)))
-    );
+    rec.log("segmentation/image", rerun::SegmentationImage({HEIGHT, WIDTH}, std::move(data)));
 }

docs/code-examples/depth_image_3d.cpp

@@ -0,0 +1,35 @@
+// Create and log a depth image.
+
+#include <rerun.hpp>
+
+#include <algorithm>
+
+int main() {
+    auto rec = rerun::RecordingStream("rerun_example_depth_image");
+    rec.connect("127.0.0.1:9876").throw_on_failure();
+
+    // Create a synthetic depth image.
+    const int HEIGHT = 8;
+    const int WIDTH = 12;
+    std::vector<uint16_t> data(WIDTH * HEIGHT, 65535);
+    for (auto y = 0; y < 4; ++y) {                       // top half
+        std::fill_n(data.begin() + y * WIDTH, 6, 20000); // left half
+    }
+    for (auto y = 4; y < 8; ++y) {                           // bottom half
+        std::fill_n(data.begin() + y * WIDTH + 6, 6, 45000); // right half
+    }
+
+    // If we log a pinhole camera model, the depth gets automatically back-projected to 3D
+    rec.log(
+        "world/camera",
+        rerun::Pinhole::focal_length_and_resolution(
+            {20.0f, 20.0f},
+            {static_cast<float>(WIDTH), static_cast<float>(HEIGHT)}
+        )
+    );
+
+    rec.log(
+        "world/camera/depth",
+        rerun::DepthImage({HEIGHT, WIDTH}, std::move(data)).with_meter(10000.0)
+    );
+}

docs/code-examples/depth_image_simple.cpp

@@ -0,0 +1,23 @@
+// Create and log a depth image.
+
+#include <rerun.hpp>
+
+#include <algorithm>
+
+int main() {
+    auto rec = rerun::RecordingStream("rerun_example_depth_image");
+    rec.connect("127.0.0.1:9876").throw_on_failure();
+
+    // create a synthetic depth image.
+    const int HEIGHT = 8;
+    const int WIDTH = 12;
+    std::vector<uint16_t> data(WIDTH * HEIGHT, 65535);
+    for (auto y = 0; y < 4; ++y) {                       // top half
+        std::fill_n(data.begin() + y * WIDTH, 6, 20000); // left half
+    }
+    for (auto y = 4; y < 8; ++y) {                           // bottom half
+        std::fill_n(data.begin() + y * WIDTH + 6, 6, 45000); // right half
+    }
+
+    rec.log("depth", rerun::DepthImage({HEIGHT, WIDTH}, std::move(data)).with_meter(10000.0));
+}

docs/code-examples/image_simple.cpp

@@ -0,0 +1,25 @@
+// Create and log a image.
+
+#include <rerun.hpp>
+
+int main() {
+    auto rec = rerun::RecordingStream("rerun_example_image_simple");
+    rec.connect("127.0.0.1:9876").throw_on_failure();
+
+    // Create a synthetic image.
+    const int HEIGHT = 8;
+    const int WIDTH = 12;
+    std::vector<uint8_t> data(WIDTH * HEIGHT * 3, 0);
+    for (size_t i = 0; i < data.size(); i += 3) {
+        data[i] = 255;
+    }
+    for (auto y = 0; y < 4; ++y) { // top half
+        auto row = data.begin() + y * WIDTH * 3;
+        for (auto i = 0; i < 6 * 3; i += 3) { // left half
+            row[i] = 0;
+            row[i + 1] = 255;
+        }
+    }
+
+    rec.log("image", rerun::Image({HEIGHT, WIDTH, 3}, std::move(data)));
+}

docs/code-examples/roundtrips.py

@@ -23,16 +23,11 @@
     "any_values": ["cpp", "rust"], # Not yet implemented
     "asset3d_out_of_tree": ["cpp"], # TODO(#2919): Not yet implemented in C++
     "custom_data": ["cpp"], # TODO(#2919): Not yet implemented in C++
-    "depth_image_3d": ["cpp"], # TODO(#2919): Not yet implemented in C++
-    "depth_image_simple": ["cpp"],  # TODO(#2919): Not yet implemented in C++
     "extra_values": ["cpp", "rust"], # Missing examples
     "image_advanced": ["cpp", "rust"], # Missing examples
-    "image_simple": ["cpp"], # TODO(#2919): Not yet implemented in C++
     "log_line": ["cpp", "rust", "py"], # Not a complete example -- just a single log line
     "quick_start_connect": ["cpp"], # TODO(#3870): Not yet implemented in C++
     "scalar_multiple_plots": ["cpp"], # TODO(#2919): Not yet implemented in C++
-    "segmentation_image_simple": ["cpp"], # TODO(#2919): Not yet implemented in C++
-    "tensor_simple": ["cpp"], # TODO(#2919): Not yet implemented in C++
     "text_log_integration": ["cpp"], # TODO(#2919): Not yet implemented in C++
 
     # This is this script, it's not an example.

docs/code-examples/segmentation_image_simple.cpp

@@ -0,0 +1,32 @@
+// Create and log a segmentation image.
+
+#include <rerun.hpp>
+
+#include <algorithm>
+
+int main() {
+    auto rec = rerun::RecordingStream("rerun_example_annotation_context_connections");
+    rec.connect("127.0.0.1:9876").throw_on_failure();
+
+    // Create a segmentation image
+    const int HEIGHT = 8;
+    const int WIDTH = 12;
+    std::vector<uint8_t> data(WIDTH * HEIGHT, 0);
+    for (auto y = 0; y < 4; ++y) {                   // top half
+        std::fill_n(data.begin() + y * WIDTH, 6, 1); // left half
+    }
+    for (auto y = 4; y < 8; ++y) {                       // bottom half
+        std::fill_n(data.begin() + y * WIDTH + 6, 6, 2); // right half
+    }
+
+    // create an annotation context to describe the classes
+    rec.log_timeless(
+        "/",
+        rerun::AnnotationContext({
+            rerun::AnnotationInfo(1, "red", rerun::Rgba32(255, 0, 0)),
+            rerun::AnnotationInfo(2, "green", rerun::Rgba32(0, 255, 0)),
+        })
+    );
+
+    rec.log("image", rerun::SegmentationImage({HEIGHT, WIDTH}, std::move(data)));
+}

docs/code-examples/tensor_simple.cpp

@@ -0,0 +1,21 @@
+// Create and log a tensor.
+
+#include <rerun.hpp>
+
+#include <random>
+
+int main() {
+    auto rec = rerun::RecordingStream("rerun_example_tensor_simple");
+    rec.connect("127.0.0.1:9876").throw_on_failure();
+
+    std::default_random_engine gen;
+    std::uniform_int_distribution<uint8_t> dist(0, 255);
+
+    std::vector<uint8_t> data(8 * 6 * 3 * 5);
+    std::generate(data.begin(), data.end(), [&] { return dist(gen); });
+
+    rec.log(
+        "tensor",
+        rerun::Tensor({8, 6, 3, 5}, data).with_dim_names({"batch", "channel", "height", "width"})
+    );
+}

docs/code-examples/tensor_simple.rs

@@ -9,7 +9,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let mut data = Array::<u8, _>::default((8, 6, 3, 5).f());
     data.map_inplace(|x| *x = rand::random());
 
-    let tensor = rerun::Tensor::try_from(data)?.with_names(["batch", "channel", "height", "width"]);
+    let tensor =
+        rerun::Tensor::try_from(data)?.with_dim_names(["batch", "channel", "height", "width"]);
     rec.log("tensor", &tensor)?;
 
     rerun::native_viewer::show(storage.take())?;