OPENCV Learning notes Read, modify, save images

Direct attached program and Effect diagram:

#include <opencv2/opencv.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/ highgui.hpp>
#include <iostream>

using namespace std;
using namespace CV;

int main (int argc,char** argv)
{
	
	Mat img;//original image
	Img=imread ("1.jpg", Cv_load_image_color);

	if (! Img.data)
	{
		cout<< "could not open" <<endl;
		return-1;
	}
	Mat gray_img;//Grayscale Image
	Cvtcolor (img,gray_img,cv_bgr2gray);

	Imwrite ("Gray_img.jpg", gray_img);

	Namedwindow ("Img", window_autosize);
	Namedwindow ("Gray_img", window_autosize);
	
	Imshow ("IMG", IMG);
	Imshow ("Gray_img", gray_img);
	Waitkey (0);

	return 0;
}

Analytical:

1, first, must contain the necessary library files and avoid naming duplicates;

2. Imread function: Loads an image from a file

C + +: Mat imread (const string& filename, int flags=1)

      python: cv2.imread (filename[, flags])  →retval  

        Parameters:   filename  –name of file to be Loaded.
                 flags  –flags specifying the color Type of a loaded image:                       Cv_load_imag E_anydepth -If set, return 16-bit/32-bit image when the input has the corresponding depth, otherwise convert it To 8-bit.
                      Cv_load_image_color -I F set, always convert image to the color one
                    &N Bsp Cv_load_image_grayscale -If set, always convert IMAGE to the grayscale one
    &N Bsp                 >0  return a 3-channel color image.

Note

The current implementation The alpha channel, if any, was stripped from the output image. Use negative value if you need the alpha channel.
=0 Return a grayscale image.
<0 Return the loaded image as is (with alpha channel).

3. Cvtcolor function: Converts an image from one color space to another.
C + +: void Cvtcolor (Inputarray src, outputarray dst, int code, int dstcn=0)

Python:cv2.cvtColor (SRC, code[, dst[, DSTCN]) →dst

Parameters: src–input image:8-bit unsigned, 16-bit unsigned (Cv_16uc ...), or single-precision floating-point.
DST–output image of the same size and depth as SRC.
Code–color Space Conversion Code (RGB GRAY (Cv_bgr2gray,cv_rgb2gray,cv_gray2bgr,cv_gray2rgb)RGB YCRCB (Cv_bgr2ycrcb,cv_rgb2ycrcb,cv_ycrcb2bgr,cv_ycrcb2rgb) RGB HSV (Cv_bgr2hsv,cv_rgb2hsv,cv_hsv2bgr,cv_hsv2rgb )).
DSTCN–number of channels in the destination image; If the parameter is 0, the number of the channels was derived automatically from SRC and code 4, Imwrite function: Saves an IMA GE to a specified file.

C + +: BOOL Imwrite (const string& filename, inputarray img, const vector<in t>& params=vector<int> ())

Python:cv2.imwrite (filename, img[, params]) →retval

Parameters: filename –name of the file.
img –image to be saved.
params –format-specific Save parameters encoded as pairs paramid_1, paramvalue_1,

Paramid_2, paramvalue_2, .... The following parameters is currently supported:for JPEG, it can b e a quality (cv_imwrite_jpeg_quality) from 0 to + (the higher is the better). Default value is 95.
For PNG, it can being the compression level (Cv_imwrite_png_compression) from 0 to 9. A higher value means a smaller size and longer compression time. Default value is 3.
For PPM, PGM, or PBM, it can be a binary format flag (cv_imwrite_pxm_bin ARY), 0 or 1. Default value is 1.