update decoder

Makefile

@@ -27,6 +27,12 @@ else
 	CFLAGS+= -DCXXNET_USE_OPENCV=0
 endif
 
+ifeq ($(USE_OPENCV_DECODER),1)
+	CFLAGS+= -DCXXNET_USE_OPENCV_DECODER=1
+else
+	CFLAGS+= -DCXXNET_USE_OPENCV_DECODER=0
+endif
+
 # customize cudnn path
 ifneq ($(USE_CUDNN_PATH), NONE)
 	CFLAGS += -I$(USE_CUDNN_PATH)

make/config.mk

@@ -25,8 +25,8 @@ USE_CUDA_PATH = NONE
 # you can disable it, however, you will not able to use
 # imbin iterator
 USE_OPENCV = 1
-
-# whether use CUDNN R2 library
+USE_OPENCV_DECODER = 1
+# whether use CUDNN R3 library
 USE_CUDNN = 0
 # add the path to CUDNN libary to link and compile flag
 # if you do not need that, or do not have that, leave it as NONE

src/utils/decoder.h

@@ -101,11 +101,7 @@ struct JpegDecoder {
 #if CXXNET_USE_OPENCV
 struct OpenCVDecoder {
   void Decode(unsigned char *ptr, size_t sz, mshadow::TensorContainer<cpu, 3, unsigned char> *p_data) {
-    // can be improved without memcpy buf
-    cv::Mat buf(0, 0, CV_8U);
-    buf.data = ptr;
-    buf.rows = 1;
-    buf.cols = sz;
+    cv::Mat buf(1, sz, CV_8U, ptr);
     cv::Mat res = cv::imdecode(buf, 1);
     utils::Assert(res.data != NULL, "decoding fail");
     p_data->Resize(mshadow::Shape3(res.rows, res.cols, 3));