opencv学习（五）调整图像的亮度和对比度

调整图像亮度和对比度的操作属于像素操作–点操作： 

                                                  g(i,j)=αf(i,j)+β,其中α>0,β是增益变量g(i,j)=αf(i,j)+β,其中α>0,β是增益变量

代码如下：

int main(int argc, char** argv) {
	Mat src, dst;
	src = imread("D:/vcprojects/images/test.png");
	if (!src.data) {
		printf("could not load image...\n");
		return -1;
	}
	char input_win[] = "input image";
	cvtColor(src, src, CV_BGR2GRAY);
	imshow(input_win, src);

	// contrast and brigthtness changes 
	int height = src.rows;
	int width = src.cols;
	dst = Mat::zeros(src.size(), src.type());
	float alpha = 1.2;
	float beta = 30;

	for (int i = 0; i < height; i++) {
		for (int j = 0; j < width; j++) {
			if (src.channels() == 3) {
				int b = src.at<Vec3b>(i, j)[0];
				int g = src.at<Vec3b>(i, j)[1]; 
				int r = src.at<Vec3b>(i, j)[2]; 

				dst.at<Vec3b>(i, j)[0] = saturate_cast<uchar>(b*alpha + beta);
				dst.at<Vec3b>(i, j)[1] = saturate_cast<uchar>(g*alpha + beta);
				dst.at<Vec3b>(i, j)[2] = saturate_cast<uchar>(r*alpha + beta);
			}
			else if (src.channels() == 1) {
				float v = src.at<uchar>(i, j);
				dst.at<uchar>(row, col) = saturate_cast<uchar>(v*alpha + beta);
			}
		}
	}

	char output_title[] = "contrast and brightness change demo";
	imshow(output_title, dst);

	waitKey(0);
	return 0;
}

注意：int 改为float时候

float b = src.at<Vec3f>(i,j)[0];
float g = src.at<Vec3f>(i,j)[1];
float r = src.at<Vec3f>(i,j)[2];

需要把图片改为float

src.convertTo(src,CV_32F);