SPNG integration warning fixes.

modules/imgcodecs/src/grfmt_spng.cpp

@@ -521,7 +521,6 @@ int SPngEncoder::writeDataToBuf(void *ctx, void *user, void *dst_src, size_t len
 
 bool SPngEncoder::write(const Mat &img, const std::vector<int> &params)
 {
-    int fmt;
     spng_ctx *ctx = spng_ctx_new(SPNG_CTX_ENCODER);
     FILE *volatile f = 0;
     int width = img.cols, height = img.rows;
@@ -558,11 +557,10 @@ bool SPngEncoder::write(const Mat &img, const std::vector<int> &params)
                 isBilevel = params[i + 1] != 0;
             }
         }
-        fmt = channels == 1 ? SPNG_COLOR_TYPE_GRAYSCALE : channels == 3 ? SPNG_COLOR_TYPE_TRUECOLOR
-                                                                        : SPNG_COLOR_TYPE_TRUECOLOR_ALPHA;
 
         ihdr.bit_depth = depth == CV_8U ? isBilevel ? 1 : 8 : 16;
-        ihdr.color_type = fmt;
+        ihdr.color_type = (uint8_t)(channels == 1 ? SPNG_COLOR_TYPE_GRAYSCALE : channels == 3 ? SPNG_COLOR_TYPE_TRUECOLOR
+                                                                                              : SPNG_COLOR_TYPE_TRUECOLOR_ALPHA);
         ihdr.interlace_method = SPNG_INTERLACE_NONE;
         ihdr.filter_method = SPNG_FILTER_NONE;
         ihdr.compression_method = 0;
@@ -597,7 +595,7 @@ bool SPngEncoder::write(const Mat &img, const std::vector<int> &params)
             ret = spng_encode_image(ctx, nullptr, 0, SPNG_FMT_PNG, SPNG_ENCODE_PROGRESSIVE);
             if (channels > 1)
             {
-                int error;
+                int error = SPNG_OK;
                 if (ret == SPNG_OK)
                 {
                     if (depth == CV_16U)
@@ -659,7 +657,7 @@ bool SPngEncoder::write(const Mat &img, const std::vector<int> &params)
             }
             else
             {
-                int error;
+                int error = SPNG_OK;
                 for (int y = 0; y < height; y++)
                 {
                     error = spng_encode_row(ctx, img.data + y * img.step, width * channels * (depth == CV_16U ? 2 : 1));
@@ -711,17 +709,17 @@ void spngCvt_BGRA2Gray_8u_C4C1R(const uchar *bgra, int rgba_step,
                                 uchar *gray, int gray_step,
                                 cv::Size size, int _swap_rb)
 {
-    int i;
     for (; size.height--; gray += gray_step)
     {
         double cBGR0 = 0.1140441895;
+        double cBGR1 = 0.5869750977;
         double cBGR2 = 0.2989807129;
+
         if (_swap_rb)
             std::swap(cBGR0, cBGR2);
-        for (i = 0; i < size.width; i++, bgra += 4)
+        for (int i = 0; i < size.width; i++, bgra += 4)
         {
-            int t = cBGR0 * bgra[0] + 0.5869750977 * bgra[1] + cBGR2 * bgra[2];
-            gray[i] = (uchar)t;
+            gray[i] = cv::saturate_cast<uchar>(cBGR0 * bgra[0] + cBGR1 * bgra[1] + cBGR2 * bgra[2]);
         }
 
         bgra += rgba_step - size.width * 4;
@@ -732,17 +730,17 @@ void spngCvt_BGRA2Gray_16u_CnC1R(const ushort *bgr, int bgr_step,
                                  ushort *gray, int gray_step,
                                  cv::Size size, int ncn, int _swap_rb)
 {
-    int i;
     for (; size.height--; gray += gray_step)
     {
         double cBGR0 = 0.1140441895;
+        double cBGR1 = 0.5869750977;
         double cBGR2 = 0.2989807129;
+
         if (_swap_rb)
             std::swap(cBGR0, cBGR2);
-        for (i = 0; i < size.width; i++, bgr += ncn)
+        for (int i = 0; i < size.width; i++, bgr += ncn)
         {
-            int t = cBGR0 * bgr[0] + 0.5869750977 * bgr[1] + cBGR2 * bgr[2];
-            gray[i] = (ushort)t;
+            gray[i] = (ushort)(cBGR0 * bgr[0] + cBGR1 * bgr[1] + cBGR2 * bgr[2]);
         }
 
         bgr += bgr_step - size.width * ncn;