row_idx           182 ext/gd/libgd/webpimg.c   int x, y, row_idx;
row_idx           188 ext/gd/libgd/webpimg.c     row_idx = y * y_width;
row_idx           190 ext/gd/libgd/webpimg.c       double diff = Y1[row_idx + x] - Y2[row_idx + x];
row_idx           196 ext/gd/libgd/webpimg.c     row_idx = y * uv_width;
row_idx           198 ext/gd/libgd/webpimg.c       const double diff_U = U1[row_idx + x] - U2[row_idx + x];
row_idx           199 ext/gd/libgd/webpimg.c       const double diff_V = V1[row_idx + x] - V2[row_idx + x];