colmap · ahojnnes · Aug 29, 2025 · Aug 28, 2025 · Aug 28, 2025 · Aug 28, 2025
diff --git a/src/colmap/controllers/automatic_reconstruction.cc b/src/colmap/controllers/automatic_reconstruction.cc
@@ -96,6 +96,7 @@ AutomaticReconstructionController::AutomaticReconstructionController(
 
   ImageReaderOptions& reader_options = *option_manager_.image_reader;
   reader_options.image_path = *option_manager_.image_path;
+  reader_options.as_rgb = option_manager_.feature_extraction->RequiresRGB();
   if (!options_.mask_path.empty()) {
     reader_options.mask_path = options_.mask_path;
     option_manager_.image_reader->mask_path = options_.mask_path;

diff --git a/src/colmap/controllers/image_reader.cc b/src/colmap/controllers/image_reader.cc
@@ -135,7 +135,7 @@ ImageReader::Status ImageReader::Next(Rig* rig,
   // Read image.
   //////////////////////////////////////////////////////////////////////////////
 
-  if (!bitmap->Read(image_path, false)) {
+  if (!bitmap->Read(image_path, /*as_rgb=*/options_.as_rgb)) {
     return Status::BITMAP_ERROR;
   }
 

diff --git a/src/colmap/controllers/image_reader.h b/src/colmap/controllers/image_reader.h
@@ -82,6 +82,9 @@ struct ImageReaderOptions {
   // value `default_focal_length_factor * max(width, height)`.
   double default_focal_length_factor = 1.2;
 
+  // Whether to read images as grayscale or RGB.
+  bool as_rgb = false;
+
   bool Check() const;
 };
 

diff --git a/src/colmap/controllers/image_reader_test.cc b/src/colmap/controllers/image_reader_test.cc
@@ -40,35 +40,36 @@
 namespace colmap {
 namespace {
 
-Bitmap CreateTestBitmap() {
+Bitmap CreateTestBitmap(bool as_rgb) {
   Bitmap bitmap;
-  bitmap.Allocate(1, 3, false);
+  bitmap.Allocate(1, 3, as_rgb);
   bitmap.SetPixel(0, 0, BitmapColor<uint8_t>(1));
   bitmap.SetPixel(1, 0, BitmapColor<uint8_t>(2));
   bitmap.SetPixel(2, 0, BitmapColor<uint8_t>(3));
   return bitmap;
 }
 
 class ParameterizedImageReaderTests
-    : public ::testing::TestWithParam<
-          std::tuple</*num_images=*/int,
-                     /*with_masks=*/bool,
-                     /*with_existing_images=*/bool>> {};
+    : public ::testing::TestWithParam<std::tuple</*num_images=*/int,
+                                                 /*with_masks=*/bool,
+                                                 /*with_existing_images=*/bool,
+                                                 /*as_rgb=*/bool>> {};
 
 TEST_P(ParameterizedImageReaderTests, Nominal) {
-  const auto [kNumImages, kWithMasks, kWithExistingImages] = GetParam();
+  const auto [kNumImages, kWithMasks, kWithExistingImages, kAsRGB] = GetParam();
 
   auto database = Database::Open(kInMemorySqliteDatabasePath);
 
   const std::string test_dir = CreateTestDir();
   ImageReaderOptions options;
   options.image_path = test_dir + "/images";
+  options.as_rgb = kAsRGB;
   CreateDirIfNotExists(options.image_path);
   if (kWithMasks) {
     options.mask_path = test_dir + "/masks";
     CreateDirIfNotExists(options.mask_path);
   }
-  const Bitmap test_bitmap = CreateTestBitmap();
+  const Bitmap test_bitmap = CreateTestBitmap(kAsRGB);
   for (int i = 0; i < kNumImages; ++i) {
     const std::string image_name = std::to_string(i) + ".png";
     test_bitmap.Write(options.image_path + "/" + image_name);
@@ -117,6 +118,7 @@ TEST_P(ParameterizedImageReaderTests, Nominal) {
     EXPECT_EQ(camera.width, test_bitmap.Width());
     EXPECT_EQ(camera.height, test_bitmap.Height());
     EXPECT_EQ(image.Name(), std::to_string(i) + ".png");
+    EXPECT_EQ(bitmap.IsRGB(), kAsRGB);
     EXPECT_EQ(bitmap.ConvertToRowMajorArray(),
               test_bitmap.ConvertToRowMajorArray());
     if (kWithExistingImages) {
@@ -135,12 +137,29 @@ TEST_P(ParameterizedImageReaderTests, Nominal) {
   EXPECT_EQ(database->NumCameras(), kNumImages);
 }
 
-INSTANTIATE_TEST_SUITE_P(ImageReaderTests,
-                         ParameterizedImageReaderTests,
-                         ::testing::Values(std::make_tuple(0, false, true),
-                                           std::make_tuple(5, false, false),
-                                           std::make_tuple(5, true, false),
-                                           std::make_tuple(5, false, true)));
+INSTANTIATE_TEST_SUITE_P(
+    ImageReaderTests,
+    ParameterizedImageReaderTests,
+    ::testing::Values(std::make_tuple(/*num_images=*/0,
+                                      /*with_masks=*/false,
+                                      /*with_existing_images=*/true,
+                                      /*as_rgb=*/true),
+                      std::make_tuple(/*num_images=*/5,
+                                      /*with_masks=*/false,
+                                      /*with_existing_images=*/false,
+                                      /*as_rgb=*/true),
+                      std::make_tuple(/*num_images=*/5,
+                                      /*with_masks=*/true,
+                                      /*with_existing_images=*/false,
+                                      /*as_rgb=*/true),
+                      std::make_tuple(/*num_images=*/5,
+                                      /*with_masks=*/true,
+                                      /*with_existing_images=*/false,
+                                      /*as_rgb=*/false),
+                      std::make_tuple(/*num_images=*/5,
+                                      /*with_masks=*/false,
+                                      /*with_existing_images=*/true,
+                                      /*as_rgb=*/true)));
 
 }  // namespace
 }  // namespace colmap
diff --git a/src/colmap/exe/feature.cc b/src/colmap/exe/feature.cc
@@ -106,6 +106,7 @@ int RunFeatureExtractor(int argc, char** argv) {
 
   ImageReaderOptions reader_options = *options.image_reader;
   reader_options.image_path = *options.image_path;
+  reader_options.as_rgb = options.feature_extraction->RequiresRGB();
 
   if (camera_mode >= 0) {
     UpdateImageReaderOptionsFromCameraMode(reader_options,

diff --git a/src/colmap/feature/extractor.cc b/src/colmap/feature/extractor.cc
@@ -46,6 +46,16 @@ void ThrowUnknownFeatureExtractorType(FeatureExtractorType type) {
 FeatureExtractionOptions::FeatureExtractionOptions(FeatureExtractorType type)
     : type(type), sift(std::make_shared<SiftExtractionOptions>()) {}
 
+bool FeatureExtractionOptions::RequiresRGB() const {
+  switch (type) {
+    case FeatureExtractorType::SIFT:
+      return false;
+    default:
+      ThrowUnknownFeatureExtractorType(type);
+  }
+  return false;
+}
+
 bool FeatureExtractionOptions::Check() const {
   CHECK_OPTION_GT(max_image_size, 0);
   if (use_gpu) {

diff --git a/src/colmap/feature/extractor.h b/src/colmap/feature/extractor.h
@@ -62,6 +62,9 @@ struct FeatureExtractionOptions {
 
   std::shared_ptr<SiftExtractionOptions> sift;
 
+  // Whether the selected extractor requires RGB (or grayscale) images.
+  bool RequiresRGB() const;
+
   bool Check() const;
 };
 

diff --git a/src/colmap/ui/feature_extraction_widget.cc b/src/colmap/ui/feature_extraction_widget.cc
@@ -115,6 +115,7 @@ void SIFTExtractionWidget::Run() {
 
   ImageReaderOptions reader_options = *options_->image_reader;
   reader_options.image_path = *options_->image_path;
+  reader_options.as_rgb = options_->feature_extraction->RequiresRGB();
 
   auto extractor = CreateFeatureExtractorController(
       *options_->database_path, reader_options, *options_->feature_extraction);