批量删除LabelImg制作的.xml中的部分的节点值（标签值）

蔚落 2021-12-01 16:14 325阅读 0赞

## 概述 ##

自己在用labelImg打好标签后，想只用其中几类训练，不想训练全部类别，又不想重新打标生成.xml文件，因此想到这个办法：**直接在.xml文件中删除原有的不需要的标签类及其属性。**

打标时标签名出现了大小写（工程量大时可能会手滑），程序中有改写标签值为小写的过程，因为我做py-faster-rcnn 训练时，标签必须全部为小写。

以如下的.xml文件为例，我故意把标签增加了大写

<annotation verified="yes">
    	<filename>test.jpg</filename>
    	<path>C:\Users\yasin\Desktop\test</path>
    	<source>
    		<database>Unknown</database>
    	</source>
    	<size>
    		<width>400</width>
    		<height>300</height>
    		<depth>3</depth>
    	</size>
    	<segmented>0</segmented>
    	<object>
    		<name>People</name>
    		<pose>Unspecified</pose>
    		<truncated>0</truncated>
    		<difficult>0</difficult>
    		<bndbox>
    			<xmin>80</xmin>
    			<ymin>69</ymin>
    			<xmax>144</xmax>
    			<ymax>89</ymax>
    		</bndbox>
    	</object>
    	<object>
    		<name>CAT</name>
    		<pose>Unspecified</pose>
    		<truncated>0</truncated>
    		<difficult>0</difficult>
    		<bndbox>
    			<xmin>40</xmin>
    			<ymin>69</ymin>
    			<xmax>143</xmax>
    			<ymax>16</ymax>
    		</bndbox>
    	</object>
    	<object>
    		<name>dog</name>
    		<pose>Unspecified</pose>
    		<truncated>0</truncated>
    		<difficult>0</difficult>
    		<bndbox>
    			<xmin>96</xmin>
    			<ymin>82</ymin>
    			<xmax>176</xmax>
    			<ymax>87</ymax>
    		</bndbox>
    	</object>	
    </annotation>

## 具体实现 ##

假如我们只想保留图片上的people和cat类，其他都删除，代码如下：

from xml.etree.ElementTree import ElementTree
    from os import walk, path
    
    def read_xml(in_path):
        tree = ElementTree()
        tree.parse(in_path)
        return tree
    
    def write_xml(tree, out_path):
        tree.write(out_path, encoding="utf-8", xml_declaration=True)
    
    def find_nodes(tree, path):
        return tree.findall(path)
    
    def del_node_by_target_classes(nodelist, target_classes_lower, tree_root):
        for parent_node in nodelist:
            children = parent_node.getchildren()
            if (parent_node.tag == "object" and children[0].text.lower() not in target_classes_lower):
                tree_root.remove(parent_node)
            elif (parent_node.tag == "object" and children[0].text.lower() in target_classes_lower):
                children[0].text = children[0].text.lower()
    
    def get_path_prex(rootdir):
        data_path = []
        prefixs = []
        for root, dirs, files in walk(rootdir, topdown=True):
            for name in files:
                pre, ending = path.splitext(name)
                if ending != ".xml":
                    continue
                else:
                    data_path.append(path.join(root, name))
                    prefixs.append(pre)
    
        return data_path, prefixs
    
    if __name__ == "__main__":
        # get all the xml paths, prefixes if not used here
        paths_xml, prefixs = get_path_prex("/home/yasin/old_labels/")
    
        target_classes = ["PEOPLE", "CAT"] # target flags you want to keep
    
        target_classes_lower = []
        for i in range(len(target_classes)):
            target_classes_lower.append(target_classes[i].lower()) # make sure your target is lowe-case
    
        # print(target_classes_lower)
        for i in range(len(paths_xml)):
            # rename and save the corresponding xml
            tree = read_xml(paths_xml[i])
            
            # get tree node
            tree_root = tree.getroot()
    
            # get parent nodes
            del_parent_nodes = find_nodes(tree, "./")
            
            # get target classes and delete
            target_del_node = del_node_by_target_classes(del_parent_nodes, target_classes_lower, tree_root)
            
            # save output xml, 000001.xml
            write_xml(tree, "/home/yasin/new_labels/{}.xml".format("%06d" % i))

按照上述代码，示例.xml变为如下.xml，可以看出我们删除了除people和cat类的类别（即dog类），并把保留类别的打标改成了小写：

<?xml version='1.0' encoding='utf-8'?>
    <annotation verified="yes">
    	<filename>test.jpg</filename>
    	<path>C:\Users\yasin\Desktop\test</path>
    	<source>
    		<database>Unknown</database>
    	</source>
    	<size>
    		<width>400</width>
    		<height>300</height>
    		<depth>3</depth>
    	</size>
    	<segmented>0</segmented>
    	<object>
    		<name>people</name>
    		<pose>Unspecified</pose>
    		<truncated>0</truncated>
    		<difficult>0</difficult>
    		<bndbox>
    			<xmin>80</xmin>
    			<ymin>69</ymin>
    			<xmax>144</xmax>
    			<ymax>89</ymax>
    		</bndbox>
    	</object>
    	<object>
    		<name>cat</name>
    		<pose>Unspecified</pose>
    		<truncated>0</truncated>
    		<difficult>0</difficult>
    		<bndbox>
    			<xmin>40</xmin>
    			<ymin>69</ymin>
    			<xmax>143</xmax>
    			<ymax>16</ymax>
    		</bndbox>
    	</object>
    </annotation>