[人工智能]【Opencv&Cpp】04 像素下的图像：图像像素的读写操作、反色操作

mat.at<uchar>(row, col)

mat.at<Vec3b>(row, col)

image.ptr<uchar>(row)

?图像像素的读写操作主要是像素遍历与访问

• 数组遍历
• 指针遍历

数组遍历

灰度图像

int pv = image.at<uchar>(row, col); //读取图片像素灰度值
image.at<uchar>(row, col) = 255 - pv;? ?//取反

彩色图像

Vec3b bgr = image.at<Vec3b>(row, col);? ?//三通道的
image.at<Vec3b>(row, col)[0] = 255 - bgr[0];
image.at<Vec3b>(row, col)[1] = 255 - bgr[1];
image.at<Vec3b>(row, col)[2] = 255 - bgr[2];

?

int w = image.cols; //列数
	int h = image.rows;//行数
	int dims = image.channels();//通道数

	for (int row = 0; row < h; row++) {
		for (int col = 0; col < w; col++) {
			if (dims == 1) { // 灰度图像
				int pv = image.at<uchar>(row, col);
				image.at<uchar>(row, col) = 255 - pv;
			}
			if (dims == 3) { // 彩色图像
				Vec3b bgr = image.at<Vec3b>(row, col);
				image.at<Vec3b>(row, col)[0] = 255 - bgr[0];
				image.at<Vec3b>(row, col)[1] = 255 - bgr[1];
				image.at<Vec3b>(row, col)[2] = 255 - bgr[2];
			}
		}
	}

?

指针遍历

for (int row = 0; row < h; row++) {
		uchar* current_row = image.ptr<uchar>(row);
		for (int col = 0; col < w; col++) {
			if (dims == 1) { // 灰度图像
				int pv = *current_row;
				*current_row++ = 255 - pv;  // 赋值之后，指针后移
			}
			if (dims == 3) { // 彩色图像
				*current_row++ = 255 - *current_row;
				*current_row++ = 255 - *current_row;
				*current_row++ = 255 - *current_row;
			}
		}
	}

结果一样

?