图像预处理少不了阈值分割，去除不需要的图片特征，增强图片的目标特征，halcon有一系列操作算子。啃纯英的说明书，真是
| auto_threshold | Segment an image using thresholds determined from its histogram. |
| binary_threshold |
Segment an image using binary thresholding. 二值化 |
| char_threshold |
Perform a threshold segmentation for extracting characters. 区分字符（有光暗阴影） |
| check_difference |
Compare two images pixel by pixel. 一个一个像素比较两张图片 |
| dual_threshold | Threshold operator for signed images. |
| dyn_threshold | Segment an image using a local threshold. |
| fast_threshold | Fast thresholding of images using global thresholds. |
| histo_to_thresh |
Determine gray value thresholds from a histogram. 灰度直方图 |
| local_threshold | Segment an image using local thresholding. |
| threshold | Segment an image using global threshold. |
| threshold_sub_pix | Extract level crossings from an image with subpixel accuracy. |
| var_threshold | Threshold an image by local mean and standard deviation analysis. |
| zero_crossing | Extract zero crossings from an image. |
| zero_crossing_sub_pix | Extract zero crossings from an image with subpixel accuracy. |
对于不同的图片，有不同的效果