Merge pull request opencv#17728 from sturkmen72:patch-4

Author: alalek

modules/imgcodecs/include/opencv2/imgcodecs.hpp

@@ -204,16 +204,17 @@ can be saved using this function, with these exceptions:
 - PNG images with an alpha channel can be saved using this function. To do this, create
 8-bit (or 16-bit) 4-channel image BGRA, where the alpha channel goes last. Fully transparent pixels
 should have alpha set to 0, fully opaque pixels should have alpha set to 255/65535 (see the code sample below).
+- Multiple images (vector of Mat) can be saved in TIFF format (see the code sample below).
 
 If the format, depth or channel order is different, use
 Mat::convertTo and cv::cvtColor to convert it before saving. Or, use the universal FileStorage I/O
 functions to save the image to XML or YAML format.
 
-The sample below shows how to create a BGRA image and save it to a PNG file. It also demonstrates how to set custom
-compression parameters:
+The sample below shows how to create a BGRA image, how to set custom compression parameters and save it to a PNG file.
+It also demonstrates how to save multiple images in a TIFF file:
 @include snippets/imgcodecs_imwrite.cpp
 @param filename Name of the file.
-@param img Image to be saved.
+@param img (Mat or vector of Mat) Image or Images to be saved.
 @param params Format-specific parameters encoded as pairs (paramId_1, paramValue_1, paramId_2, paramValue_2, ... .) see cv::ImwriteFlags
 */
 CV_EXPORTS_W bool imwrite( const String& filename, InputArray img,

samples/cpp/tutorial_code/snippets/imgcodecs_imwrite.cpp

@@ -3,7 +3,7 @@
 using namespace cv;
 using namespace std;
 
-static void createAlphaMat(Mat &mat)
+static void paintAlphaMat(Mat &mat)
 {
     CV_Assert(mat.channels() == 4);
     for (int i = 0; i < mat.rows; ++i)
@@ -21,9 +21,9 @@ static void createAlphaMat(Mat &mat)
 
 int main()
 {
-    // Create mat with alpha channel
-    Mat mat(480, 640, CV_8UC4);
-    createAlphaMat(mat);
+    Mat mat(480, 640, CV_8UC4); // Create a matrix with alpha channel
+    paintAlphaMat(mat);
+
     vector<int> compression_params;
     compression_params.push_back(IMWRITE_PNG_COMPRESSION);
     compression_params.push_back(9);
@@ -37,9 +37,18 @@ int main()
     {
         fprintf(stderr, "Exception converting image to PNG format: %s\n", ex.what());
     }
+
     if (result)
         printf("Saved PNG file with alpha data.\n");
     else
         printf("ERROR: Can't save PNG file.\n");
+
+    vector<Mat> imgs;
+    imgs.push_back(mat);
+    imgs.push_back(~mat);
+    imgs.push_back(mat(Rect(0, 0, mat.cols / 2, mat.rows / 2)));
+    imwrite("test.tiff", imgs);
+    printf("Multiple files saved in test.tiff\n");
+
     return result ? 0 : 1;
 }