Decode PPI face payloads

src/assets/ppi_header.cpp

@@ -561,4 +561,59 @@ pp::foundation::Result<PpiProjectIndex> parse_ppi_project_index(std::span<const
     });
 }
 
+pp::foundation::Result<PpiDecodedProjectImages> decode_ppi_project_images(std::span<const std::byte> bytes)
+{
+    auto project = parse_ppi_project_index(bytes);
+    if (!project) {
+        return pp::foundation::Result<PpiDecodedProjectImages>::failure(project.status());
+    }
+
+    PpiDecodedProjectImages decoded {
+        .project = project.value(),
+        .faces = {},
+    };
+    decoded.faces.reserve(decoded.project.body.summary.rgba_face_payload_count);
+
+    const auto body = bytes.subspan(decoded.project.layout.body_offset, decoded.project.layout.body_bytes);
+    for (std::size_t layer_index = 0; layer_index < decoded.project.body.layers.size(); ++layer_index) {
+        const auto& layer = decoded.project.body.layers[layer_index];
+        for (std::size_t frame_index = 0; frame_index < layer.frames.size(); ++frame_index) {
+            const auto& frame = layer.frames[frame_index];
+            for (std::size_t face_index = 0; face_index < frame.faces.size(); ++face_index) {
+                const auto& face = frame.faces[face_index];
+                if (!face.has_data) {
+                    continue;
+                }
+
+                if (face.body_payload_offset > body.size()
+                    || face.payload_bytes > body.size() - face.body_payload_offset) {
+                    return pp::foundation::Result<PpiDecodedProjectImages>::failure(
+                        pp::foundation::Status::out_of_range("PPI face payload range is outside the body"));
+                }
+
+                const auto image = decode_png_rgba8(
+                    body.subspan(face.body_payload_offset, face.payload_bytes));
+                if (!image) {
+                    return pp::foundation::Result<PpiDecodedProjectImages>::failure(image.status());
+                }
+
+                if (image.value().width != face.png_width || image.value().height != face.png_height) {
+                    return pp::foundation::Result<PpiDecodedProjectImages>::failure(
+                        pp::foundation::Status::invalid_argument("decoded PPI face payload dimensions changed"));
+                }
+
+                decoded.faces.push_back(PpiDecodedFacePayload {
+                    .layer_index = static_cast<std::uint32_t>(layer_index),
+                    .frame_index = static_cast<std::uint32_t>(frame_index),
+                    .face_index = static_cast<std::uint32_t>(face_index),
+                    .descriptor = face,
+                    .image = image.value(),
+                });
+            }
+        }
+    }
+
+    return pp::foundation::Result<PpiDecodedProjectImages>::success(std::move(decoded));
+}
+
 }