memcpy optimize copy_cut_border/copy_make_boder (#179)

* memcpy optimize copy_cut_border/copy_make_boder

* copy small border memcpy may slow

* remove unuse line

* code style

src/mat.cpp

@@ -348,10 +348,8 @@ static void copy_make_border_image(const Mat& src, Mat& dst, int top, int left,
             {
                 outptr[x] = v;
             }
-            for (; x < (left + src.w); x++)
-            {
-                outptr[x] = ptr[x - left];
-            }
+            memcpy(outptr + left, ptr, src.w * sizeof(float));
+            x += src.w;
             for (; x < w; x++)
             {
                 outptr[x] = v;
@@ -381,10 +379,8 @@ static void copy_make_border_image(const Mat& src, Mat& dst, int top, int left,
             {
                 outptr[x] = ptr[0];
             }
-            for (; x < (left + src.w); x++)
-            {
-                outptr[x] = ptr[x - left];
-            }
+            memcpy(outptr + left, ptr, src.w * sizeof(float));
+            x += src.w;
             for (; x < w; x++)
             {
                 outptr[x] = ptr[src.w - 1];
@@ -399,10 +395,8 @@ static void copy_make_border_image(const Mat& src, Mat& dst, int top, int left,
             {
                 outptr[x] = ptr[0];
             }
-            for (; x < (left + src.w); x++)
-            {
-                outptr[x] = ptr[x - left];
-            }
+            memcpy(outptr + left, ptr, src.w * sizeof(float));
+            x += src.w;
             for (; x < w; x++)
             {
                 outptr[x] = ptr[src.w - 1];
@@ -419,10 +413,8 @@ static void copy_make_border_image(const Mat& src, Mat& dst, int top, int left,
             {
                 outptr[x] = ptr[0];
             }
-            for (; x < (left + src.w); x++)
-            {
-                outptr[x] = ptr[x - left];
-            }
+            memcpy(outptr + left, ptr, src.w * sizeof(float));
+            x += src.w;
             for (; x < w; x++)
             {
                 outptr[x] = ptr[src.w - 1];
@@ -481,10 +473,7 @@ static void copy_cut_border_image(const Mat& src, Mat& dst, int top, int left)
 
     for (int y = 0; y < h; y++)
     {
-        for (int x = 0; x < w; x++)
-        {
-            outptr[x] = ptr[x];
-        }
+        memcpy(outptr, ptr, w*sizeof(float));
         outptr += w;
         ptr += src.w;
     }