gray_histo 计算直方图
原形：gray_histo(Regions, Image : : : AbsoluteHisto, RelativeHisto)
功能：计算直方图
参数：Regions：区域，要计算的区域（在image上的区域）
Image ：要计算的图形
AbsoluteHisto：绝对统计数量，比如灰阶值为0-255的有多少个像素点
RelativeHisto：比例，像素值0-255占整个图像的比例
代码示例：
*显示直方图
while (true)read_image(Image, 'D:\\2.PNG')rgb1_to_gray (Image, GrayImage)dev_display (GrayImage)wait_seconds (1)
* 产生一个矩形gen_rectangle1 (Rectangle, 0, 0, 9, 9)dev_inspect_ctrl (AbsoluteHisto)dev_inspect_ctrl (AbsoluteHisto)dev_close_inspect_ctrl (AbsoluteHisto)*1\显示原图直方图gray_histo (Rectangle, GrayImage,AbsoluteHisto, RelativeHisto)dev_open_window (0, 0, 512, 512, 'black', WindowHandle)dev_set_color ('green')gen_region_histo (Region, AbsoluteHisto, 255, 255, 1)dev_display (Region)dev_close_inspect_ctrl (AbsoluteHisto)dev_inspect_ctrl (AbsoluteHisto)dev_close_inspect_ctrl (RelativeHisto)dev_inspect_ctrl (RelativeHisto)*2\直方图均衡化后显示直方图dev_close_inspect_ctrl (AbsoluteHisto)dev_inspect_ctrl (AbsoluteHisto)dev_close_inspect_ctrl (AbsoluteHisto)equ_histo_image (GrayImage, ImageEquHisto)gray_histo (ImageEquHisto, ImageEquHisto,AbsoluteHisto, RelativeHisto)dev_open_window (0, 0, 512, 512, 'black', WindowHandle)dev_set_color ('red')gen_region_histo (Region, AbsoluteHisto, 255, 255, 1)dev_display (Region)break
endwhile
上图是给了一张全黑的图片，然后截取10*10的左上角，进行直方图计算；可以看到AbsoluteHisto下标0有100个，其他都是0
RelativeHisto下标0占比1 ，也就是100% ， 其他都是0 ， 因为一张全黑的图像素点的值都是0
