Add viewing thermal reference images

Author: olaals

api/.env.example

@@ -0,0 +1,2 @@
+# Azure storage account name for thermal reference images
+Storage__ThermalReferenceStorageAccount=<your-storage-account-name>

api/Controllers/ThermalReferenceMetadataController.cs

@@ -11,6 +11,7 @@ namespace api.Controllers;
 public class ThermalReferenceMetadataController(
     ILogger<ThermalReferenceMetadataController> logger,
     IThermalReferenceMetadataService thermalReferenceMetadataService,
+    IThermalImageService thermalImageService,
     IConfiguration configuration
 ) : ControllerBase
 {
@@ -164,6 +165,41 @@ public async Task<ActionResult> DeleteThermalReferenceMetadata([FromRoute] Guid
         }
     }
 
+    [HttpGet("id/{id}/image")]
+    [Authorize(Roles = Role.Any)]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult> GetThermalReferenceImage([FromRoute] Guid id)
+    {
+        try
+        {
+            var metadata = await thermalReferenceMetadataService.ReadById(id);
+            if (metadata is null)
+            {
+                return NotFound($"Could not find thermal reference metadata with id {id}");
+            }
+
+            var result = await thermalImageService.GetThermalImageAsJpegAsync(
+                metadata.ReferenceImageBlobStorageLocation
+            );
+
+            Response.Headers["X-Temperature-Min"] = result.MinTemperature.ToString("F2");
+            Response.Headers["X-Temperature-Max"] = result.MaxTemperature.ToString("F2");
+            Response.Headers["Access-Control-Expose-Headers"] =
+                "X-Temperature-Min, X-Temperature-Max";
+
+            return File(result.JpegBytes, "image/jpeg");
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Error generating thermal reference image for id {Id}", id);
+            return StatusCode(
+                StatusCodes.Status500InternalServerError,
+                "An error occurred while generating the thermal reference image"
+            );
+        }
+    }
+
     private (
         BlobStorageLocation imageLocation,
         BlobStorageLocation polygonLocation

api/Program.cs

@@ -70,6 +70,8 @@
 );
 
 builder.Services.AddScoped<IThermalReferenceMetadataService, ThermalReferenceMetadataService>();
+builder.Services.AddScoped<IBlobStorageService, BlobStorageService>();
+builder.Services.AddScoped<IThermalImageService, ThermalImageService>();
 builder.Services.AddScoped<IInspectionRecordService, InspectionRecordService>();
 builder.Services.AddScoped<IAnalysisService, AnalysisService>();
 builder.Services.AddScoped<IAnalysisGroupService, AnalysisGroupService>();

api/Services/BlobStorageService.cs

@@ -0,0 +1,42 @@
+using api.Database.Models;
+using Azure.Core;
+using Azure.Storage.Blobs;
+
+namespace api.Services;
+
+public interface IBlobStorageService
+{
+    Task<MemoryStream> DownloadBlobAsync(BlobStorageLocation location);
+}
+
+public class BlobStorageService(TokenCredential credential) : IBlobStorageService
+{
+    public async Task<MemoryStream> DownloadBlobAsync(BlobStorageLocation location)
+    {
+        if (string.IsNullOrWhiteSpace(location.StorageAccount))
+            throw new InvalidOperationException("BlobStorageLocation.StorageAccount is empty.");
+
+        if (string.IsNullOrWhiteSpace(location.BlobContainer))
+            throw new InvalidOperationException(
+                $"BlobStorageLocation.BlobContainer is empty for storage account '{location.StorageAccount}'."
+            );
+
+        if (string.IsNullOrWhiteSpace(location.BlobName))
+            throw new InvalidOperationException(
+                $"BlobStorageLocation.BlobName is empty for storage account '{location.StorageAccount}/{location.BlobContainer}'."
+            );
+
+        var serviceClient = new BlobServiceClient(
+            new Uri($"https://{location.StorageAccount}.blob.core.windows.net"),
+            credential
+        );
+
+        var containerClient = serviceClient.GetBlobContainerClient(location.BlobContainer);
+        var blobClient = containerClient.GetBlobClient(location.BlobName);
+
+        var stream = new MemoryStream();
+        await blobClient.DownloadToAsync(stream);
+        stream.Position = 0;
+        return stream;
+    }
+}