toCompressedImageMsg is missing full format

[christian-rauch]

Typically, the format in the CompressedImage type contains the data format and the compression algorithm, e.g.: "16UC1; png compressed " for a sensor that published depth as 16bit image.

The method toCompressedImageMsg however only sets the format:

vision_opencv/cv_bridge/src/cv_bridge.cpp

Lines 503 to 505 in 51ca543

	std::string format = getFormat(dst_format);
	ros_image.format = format;
	cv::imencode("." + format, image, ros_image.data);

hence the format will only contain png without the datatype.