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Update documentation of imwrite()

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This commit is contained in:
Suleyman TURKMEN 2020-07-01 23:50:09 +03:00 committed by sturkmen72
parent 5a7045181a
commit 2566d13100
2 changed files with 17 additions and 7 deletions
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7
modules/imgcodecs/include/opencv2/imgcodecs.hpp
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@ -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,

17
samples/cpp/tutorial_code/snippets/imgcodecs_imwrite.cpp
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@ -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;
}