!10429 Optimize ExtractChannel op for lite cv

From: @jiangzhiwen8
Reviewed-by: @xulei2020,@pandoublefeng,@heleiwang,@liucunwei
Signed-off-by: @liucunwei

mindspore/ccsrc/minddata/dataset/kernels/image/lite_cv/image_process.cc

@@ -659,42 +659,34 @@ static void PadWithConstant(const LiteMat &src, LiteMat &dst, const int top, con
   }
 }
 
-bool ExtractChannel(const LiteMat &src, LiteMat &dst, int col) {
+template <typename T>
+void ExtractChannelImpl(T *src_ptr, T *dst_ptr, int height, int width, int channel, int col) {
+  int total = height * width;
+  int i = 0;
+  int src_idx = col;
+  for (; i < total; i++, src_idx += channel) {
+    dst_ptr[i] = src_ptr[src_idx];
+  }
+}
+
+bool ExtractChannel(LiteMat &src, LiteMat &dst, int col) {
   if (src.IsEmpty() || col < 0 || col > src.channel_ - 1) {
     return false;
   }
-  if (src.data_type_ == LDataType::FLOAT32) {
-    (void)dst.Init(src.width_, src.height_, 1, src.data_type_);
-    const float *src_start_p = src;
-    float *dst_start_p = dst;
-    for (int h = 0; h < src.height_; h++) {
-      uint32_t src_start = h * src.width_ * src.channel_ + col;
-      uint32_t dst_start = h * dst.width_;
-      for (int w = 0; w < src.width_; w++) {
-        uint32_t src_index = src_start + w * src.channel_;
-        uint32_t dst_index = dst_start + w;
-        dst_start_p[dst_index] = src_start_p[src_index];
-      }
-    }
-    return true;
-  } else if (src.data_type_ == LDataType::UINT8) {
-    (void)dst.Init(src.width_, src.height_, 1, src.data_type_);
-    const uint8_t *src_start_p = src;
-    uint8_t *dst_start_p = dst;
-    for (int h = 0; h < src.height_; h++) {
-      uint32_t src_start = h * src.width_ * src.channel_ + col;
-      uint32_t dst_start = h * dst.width_;
-      for (int w = 0; w < src.width_; w++) {
-        uint32_t src_index = src_start + w * src.channel_;
-        uint32_t dst_index = dst_start + w;
-        dst_start_p[dst_index] = src_start_p[src_index];
-      }
-    }
-    return true;
+
+  if (dst.IsEmpty() || dst.width_ != src.width_ || dst.height_ != src.height_ || dst.channel_ != 1 ||
+      dst.data_type_ != src.data_type_) {
+    dst.Init(src.width_, src.height_, 1, src.data_type_);
+  }
+
+  if (dst.data_type_ == LDataType::FLOAT32) {
+    ExtractChannelImpl<float>(src, dst, src.height_, src.width_, src.channel_, col);
+  } else if (dst.data_type_ == LDataType::UINT8) {
+    ExtractChannelImpl<uint8_t>(src, dst, src.height_, src.width_, src.channel_, col);
   } else {
     return false;
   }
-  return false;
+  return true;
 }
 
 bool Split(const LiteMat &src, std::vector<LiteMat> &mv) {

mindspore/ccsrc/minddata/dataset/kernels/image/lite_cv/image_process.h

@@ -82,7 +82,7 @@ bool Pad(const LiteMat &src, LiteMat &dst, int top, int bottom, int left, int ri
          uint8_t fill_b_or_gray, uint8_t fill_g, uint8_t fill_r);
 
 /// \brief Extract image channel by index
-bool ExtractChannel(const LiteMat &src, LiteMat &dst, int col);
+bool ExtractChannel(LiteMat &src, LiteMat &dst, int col);
 
 /// \brief Split image channels to single channel
 bool Split(const LiteMat &src, std::vector<LiteMat> &mv);