Fix issue with color images and localization

This bug leads to an assertion failure when object localization is performed
on color images. This affects scripts where the DataLoader is instantiated
with target_conversion='read_contents'.

loader/src/image.hpp

@@ -268,7 +268,8 @@ friend class Video;
  createRandomAugParams(decodedDatum.size());
  transformDecodedImage(decodedDatum, datumBuf, datumLen);
  Mat decodedTarget;
- decode(encTarget, encTargetLen, &decodedTarget);
+ // Assume grayscale masks for now.
+ decodeGrayscale(encTarget, encTargetLen, &decodedTarget);
  transformDecodedImage(decodedTarget, targetBuf, targetLen);
  }
 
@@ -367,13 +368,21 @@ friend class Video;
  }
 
 private:
+ void decodeGrayscale(char* item, int itemSize, Mat* dst) {
+ Mat image(1, itemSize, CV_8UC1, item);
+ cv::imdecode(image, CV_LOAD_IMAGE_GRAYSCALE, dst);
+ }
+
+ void decodeColor(char* item, int itemSize, Mat* dst) {
+ Mat image(1, itemSize, CV_8UC3, item);
+ cv::imdecode(image, CV_LOAD_IMAGE_COLOR, dst);
+ }
+
  void decode(char* item, int itemSize, Mat* dst) {
  if (_params->_channelCount == 1) {
- Mat image(1, itemSize, CV_8UC1, item);
- cv::imdecode(image, CV_LOAD_IMAGE_GRAYSCALE, dst);
+ decodeGrayscale(item, itemSize, dst);
  } else if (_params->_channelCount == 3) {
- Mat image(1, itemSize, CV_8UC3, item);
- cv::imdecode(image, CV_LOAD_IMAGE_COLOR, dst);
+ decodeColor(item, itemSize, dst);
  } else {
  stringstream ss;
  ss << "Unsupported number of channels in image: " << _params->_channelCount;