Skills of saving images with different depths in opencv

What is image depth ？

   A lot of people start to learn OpenCV after , Several methods of contact include imwrite function , And soon know that you need to pass in a ndarray Type of mat Object as an argument , The general code is as follows ：

imwrite("D:/result.png ", dst);#dst by mat object , The previous argument is the saved address 

The image saved in this way is each channel by default 8 Bit byte image （ The size of each pixel is 0~255）, common RGB The image is an image with a depth of 24, This can be done through windows View the image properties to get , The screenshot is as follows :

If each channel occupies 16 A word of ,RGB The image depth becomes 48, If each channel occupies 32 A word of , The depth becomes 96, Obviously, the deeper the image , There will also be more image files , The more memory will be consumed when loading , therefore OpenCV The default read / write image in is each channel 8 position ( Single byte ) Images .

Preservation of various depth images

After the transformation , If you save directly , The code is as follows :

# Load image 
Mat src = imread("D:/flower.png", IMREAD_UNCHANGED);
printf("depth %d \n", src.depth());

# Convert to 16 Bit image 
Mat dst;
src.convertTo(dst, CV_16U);
imshow("flower16", dst);
imwrite("D:/flower-16.png", dst);

After the transformation , Normalize and save , The code is as follows ：

#  Load image 
Mat src = imread("D:/flower.png", IMREAD_UNCHANGED);
printf("depth %d \n", src.depth());

#  Convert to 16 Bit image 
Mat dst;
src.convertTo(dst, CV_16U);

#  Normalize and save 
normalize(dst, dst, 0, 256 * 256, NORM_MINMAX);
imwrite("D:/flower-16.png", dst);
imshow("flower-16", dst);

The comparison of the two effects is as follows ：

#  Load image 
Mat src = imread("D:/flower.png", IMREAD_UNCHANGED);
printf("depth %d \n", src.depth());

#  Convert to 32 Bit image 
Mat dst;
src.convertTo(dst, CV_32F);

#  Normalize and save 
normalize(dst, dst, 0, 1.0, NORM_MINMAX);
imwrite("D:/flower-32.png", dst);
imshow("flower-32", dst);

For the above images with different depths , It must be read correctly in the following way

Mat src = imread("D:/flower.png", IMREAD_UNCHANGED);