fix warpaffine_bilinear_yuv420sp uv matrix (#3048)

src/mat_pixel_affine.cpp

@@ -1600,9 +1600,18 @@ void warpaffine_bilinear_yuv420sp(const unsigned char* src, int srcw, int srch,
     unsigned char* dstY = dst;
     warpaffine_bilinear_c1(srcY, srcw, srch, dstY, w, h, tm, type, v_y);
 
+    const float tm_uv[6] = {
+        tm[0],
+        tm[1],
+        tm[2] / 2.0f,
+        tm[3],
+        tm[4],
+        tm[5] / 2.0f,
+    };
+
     const unsigned char* srcUV = src + srcw * srch;
     unsigned char* dstUV = dst + w * h;
-    warpaffine_bilinear_c2(srcUV, srcw / 2, srch / 2, dstUV, w / 2, h / 2, tm, type, v_uv);
+    warpaffine_bilinear_c2(srcUV, srcw / 2, srch / 2, dstUV, w / 2, h / 2, tm_uv, type, v_uv);
 }
 #endif // NCNN_PIXEL_AFFINE
 

tests/test_mat_pixel_affine.cpp

@@ -494,7 +494,7 @@ static int test_mat_pixel_affine_yuv420sp(int w, int h)
 static int test_mat_pixel_affine_1()
 {
     return 0
-           || test_mat_pixel_affine_yuv420sp(60, 40)
+           || test_mat_pixel_affine_yuv420sp(40, 40)
            || test_mat_pixel_affine_yuv420sp(120, 160)
            || test_mat_pixel_affine_yuv420sp(220, 340);
 }