创建一个程序读入并显示一幅图像

a. 允许用户在图像中选择一个矩形区域，然后通过按住鼠标画一个矩形。当鼠标放开，高亮显示矩形框，注意，在内存中保留一个原始图像的副本，以防止修改图像时改变原始图像的数据。在下一次点击鼠标按键是，恢复图像并重新开始绘制矩形

b. 在另一个独立的窗口中，使用画图函数画一个图表，分别用蓝、绿和红色表示选中每种颜色的像素数量。这是选定区域的颜色直方图。x 坐标系表示像素值范围在0-31，32-63……，223-255，y 坐标表示在选定区域中对应像素的数量。对每一个颜色通道（BGR）-Create a program to read and display an image

allows the user to select a rectangular area in the image, and then hold down the mouse to draw a rectangle. When the mouse is released, the highlighted rectangle in memory to retain a copy of the original image, to prevent modify the image to change the original image data. The next time you click the mouse button to restore the image and re-start the rectangle

in a separate window, using the drawing functions to draw a chart, said selected number of pixels of each color blue, green and red, respectively. This is the color histogram of the selected area. x coordinate system which means that the pixel value range the 0-31,32-63 ...... ,223-255, y coordinates corresponding to the number of pixels in the selected area. For each color channel (BGR)