Halcon一日一练：CAD类型的相关操作

大很多场合，需要在视觉程序中导入CAD文档，比如，在3C行业，需要对手机外壳进行CNC加工，或者点胶操作，此时，需要获取产品的各个点的数据。如果将CAD直接导入，就会大的减少编程工作量，同时也能达到很高的精度。

以下为Halcon自带例程：

* This example program shows how to read DXF files and how to
* use this CAD description of objects to generate shape models.
* The program is a slightly modified copy of the example program
* examples/hdevelop/Applications/Object-Recognition-2D/
* pm_multiple_models.hdev.
* The following modifications to this program were made:
* - The model images are created from the DXF description of
*   the objects.
* - The parameters of the operator find_shape_models were
*   slightly relaxed because the DXF object description does
*   not fit exactly to the objects in the search image because
*   the images were taken with an uncalibrated and slightly
*   oblique viewing camera.
* This program shows how to use HALCON's shape-based
* matching to find multiple different models in one call to
* find_shape_models. Note that this is one mode of operation
* that is frequently useful. However, the number of
* applications that can be solved with this mechanism is much
* larger. Other applications where finding multiple models
* in one call is useful are applications where the same object
* can only occur in small angle ranges around a discrete set
* of angles, e.g., °, °, °, and °. In these cases,
* it would be wasteful to train the model for the full °
* rotation range and to match the model in this range. Instead,
* four models using the small angle ranges around the discrete
* set of angles should be generated from the same model image
* and used in the matching stage using four different angle
* ranges.
*
dev_update_pc ('off')
dev_update_window ('off')
dev_update_var ('off')
dev_close_window ()
dev_open_window (, , , , 'black', WindowHandle)
dev_set_part (, , , )
dev_set_draw ('margin')
set_display_font (WindowHandle, , 'mono', 'true', 'false')
dev_set_line_width ()
* These colors will be used to graphically discern the different
* models in the visualization code below.
Colors := ['red','green','cyan']
* The object Models will hold a set of XLD contours that
* represent the different models. They are used below to overlay
* the found models on the current image.  XLD contours are used
* because they can be transformed much faster than regions. This
* creates a slight problem because in general multiple XLD
* contours will represent one model.  Therefore, the start and
* end indices of the different models will be stored in IndexS
* and IndexE, respectively.
gen_empty_obj (Models)
IndexS := []
IndexE := []
* The variable ModelIDs holds the different models that are
* created below.
ModelIDs := []
* Likewise, RowsRef and ColumnsRef store the reference points
* of the different models.  They are necessary to transform the
* models to the found instances in the current image.
for J :=  to  by
    dev_clear_window ()
    read_contour_xld_dxf (Contours, 'metal-part-' + J$'', [], [], DxfStatus)//读取DXF文件，并将其转换为DXF轮廓。
    gen_model_image_of_bright_object_with_holes (Contours, Image, 3.38, , )
    dev_display (Image)
    dev_set_color ('green')
    set_tposition (WindowHandle, , )
    write_string (WindowHandle, 'Generating shape model ' + J$'d')
    get_domain (Image, Domain)
    area_center (Domain, Area, Row, Column)
    * Although we will use get_shape_model_contours below to
    * obtain the representation of the model, we extract a model
    * representation here using inspect_shape_model because this
    * enables us to display the representation of the model while
    * the model is being created.
    inspect_shape_model (Image, ModelImages, ModelRegions, , )
    * Since the shape models contain a few extraneous edges,
    * they will be removed here to give a slightly nicer
    * visualization.
    connection (ModelRegions, ConnectedRegions)
    select_shape (ConnectedRegions, SelectedRegions, 'area', 'and', , )
    union1 (SelectedRegions, ModelRegions)
    gen_contours_skeleton_xld (ModelRegions, ModelContours, , 'filter')
    dev_set_color ('red')
    dev_display (ModelContours)
    create_shape_model (Image, , rad(), rad(), 'auto', 'pregeneration', 'use_polarity', , , ModelID)
    get_shape_model_contours (ModelCont, ModelID, )
    select_shape_xld (ModelCont, ModelContours, 'contlength', 'and', , )
    * Count how many XLD contours there are in the current
    * model and in the already stored models. This is necessary
    * to compute IndexS and IndexE.
    count_obj (ModelContours, NumModel)
    count_obj (Models, NumModels)
    concat_obj (Models, ModelContours, Models)
    IndexS := [IndexS,NumModels + ]
    IndexE := [IndexE,NumModels + NumModel]
    ModelIDs := [ModelIDs,ModelID]
endfor
disp_message (WindowHandle, ['Press left button to start','and stop the demo'], 'image', , , 'yellow', 'false')
get_mbutton (WindowHandle, Row1, Column1, Button1)
wait_seconds (0.5)
dev_set_color ('red')
Button :=
ImgNo :=
while (Button != )
    read_image (Image, 'metal-parts/metal-parts-' + ImgNo$'02d')
    count_seconds (S1)
    find_shape_models (Image, ModelIDs, rad(), rad(), 0.6, , 0.5, 'least_squares', , 0.3, Row, Column, Angle, Score, Model)
    count_seconds (S2)
    Time := (S2 - S1) * .
    dev_display (Image)
    Num := |Score|
    for J :=  to Num -  by
        * Select the correct XLD contours from the Models object.
        copy_obj (Models, ModelSelected, IndexS[Model[J]], IndexE[Model[J]] - IndexS[Model[J]] + )
        * Compute the transformation from the model object to
        * the current instance.
        vector_angle_to_rigid (, , , Row[J], Column[J], Angle[J], HomMat2D)
        affine_trans_contour_xld (ModelSelected, ModelTrans, HomMat2D)
        dev_set_color (Colors[Model[J]])
        dev_display (ModelTrans)
    endfor
    if (Num == )
        disp_message (WindowHandle, Num$'1d' + ' object  found in ' + Time$'4.2f' + 'ms', 'image', , , 'yellow', 'false')
    else
        disp_message (WindowHandle, Num$'1d' + ' objects found in ' + Time$'4.2f' + ' ms', 'image', , , 'yellow', 'false')
    endif
    ImgNo := ImgNo +
    if (ImgNo > )
        ImgNo :=
    endif
    dev_error_var (Error, )
    dev_set_check ('~give_error')
    get_mposition (WindowHandle, R, C, Button)
    dev_error_var (Error, )
    dev_set_check ('give_error')
    if (Error != H_MSG_TRUE)
        Button :=
    endif
endwhile
for J :=  to |ModelIDs| -  by
    clear_shape_model (ModelIDs[J])
endfor

程序中read_contour_xld_dxf 是读取DXF格式文件的算子，可以将DXF文件转换为XLD轮廓。如果没有提供文件的绝对路径，则会在当前目录下搜索DXF文件。

read_contour_xld_dxf支持如下DXF实体：多段线，2D线段，点，圆，圆弧，椭圆，块，典线。对应DXF实体的X和Y坐标分别存储在列和行的坐标。Z坐标被忽略。

输出参数DxfStatus包含有关DXF文件的部分数据，并转换为轮廓的形式输出。

我们也可以通过write_contour_xld_dxf来将XLD轮廓转换为DXF格式的CAD文件。write_contour_xld_dxf保存DXF格式时可以通过设置参数来确保数据的完整性，设置这些属性的读取可以通过设置通用参数‘read_attributes’为false来关闭，通用参数GenParamNames参数名和在GenParamValues设置的值。

DXF实体中的圆，弧，椭圆和曲线转换过程中为近似的XLD轮廓，近似精度可以通用参数min_num_points和max_approx_error来控制。参数min_num_point定义了被用于近似采样点的最小数量。需要注意的是，参数min_num_points针对完整的圆或椭圆形对应的采集点数，对应于圆弧或椭圆弧，如果min_num_points设置为50，则表示读取一个半圆，此时半圆为至少25个采样点。参数max_approx_error定义的XLD轮廓的理想圆或椭圆，分别的最大偏差（单位：pixel像素）

Halcon自带例程

* This example program shows how to use the operators
* write_contour_xld_dxf and read_contour_xld_dxf as well as
* the operators write_polygons_xld_dxf and read_polygon_xld_dxf
*
* First, edges are extracted from an image.
read_image (Image, 'mreut')
edges_sub_pix (Image, Edges, 'canny', , , )
*
* Then, to create global attributes, the regression lines are determined.
regress_contours_xld (Edges, RegressContours, 'no', )
*
* Now, we can  query what attributes and global attributes
* are available for the contours.
select_obj (RegressContours, ObjectSelected, )
query_contour_attribs_xld (ObjectSelected, Attribs)
query_contour_global_attribs_xld (ObjectSelected, GlobalAttribs)
*
* In the next step, the contours are written into a DXF file. This file
* contains also the attributes and global attributes.
write_contour_xld_dxf (RegressContours, 'contours')
*
* When the contours are read from the DXF file created with
* read_contours_xld_dxf, the (global) attributes are read, too.
read_contour_xld_dxf (ContoursRead, 'contours', [], [], DxfStatusCont)
*
* All (global) attributes that were available for the
* original contours (RegressContours) are available also for the
* contours (ContoursRead) that have been read from the DXF file.
select_obj (ContoursRead, ObjectSelected, )
query_contour_attribs_xld (ObjectSelected, AttribsTest)
query_contour_global_attribs_xld (ObjectSelected, GlobalAttribsTest)
*
* Now, we show how to write and read polygons
gen_polygons_xld (ContoursRead, Polygons, 'ramer', )
write_polygon_xld_dxf (Polygons, 'polygons')
read_polygon_xld_dxf (PolygonsRead, 'polygons', [], [], DxfStatusPoly)