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1. 组件compress功能介绍
1.1. 组件介绍：
compress是一个轻量级图像压缩库。compress允许将大照片压缩成小尺寸的鸿蒙照片，图像质量损失非常小或可以忽略不计。开件
1.2. 手机模拟器上运行效果：
2. 组件compress使用方法
2.1. 添加依赖
将compress-debug.har复制到应用的鸿蒙entry\libs目录下即可(由于build.gradle中已经依赖的libs目录下的*.har，源码下载因此不需要再做修改)。开件
2.2. 设置布局
<DependentLayout xmlns:ohos="http://schemas.huawei.com/res/ohos" ohos:width="match_parent" ohos:height="match_parent" ohos:background_element="#FFFFFF"> <Image ohos:id="$+id:image1" ohos:height="match_parent" ohos:width="match_parent" ohos:image_src="$media:dog1.PNG"/> <Text ohos:id="$+id:text" ohos:width="match_content" ohos:height="match_content" ohos:text="" ohos:text_size="19fp" ohos:text_color="#1C1C1C" ohos:top_padding="8vp" ohos:bottom_padding="8vp" ohos:right_padding="70vp" ohos:left_padding="70vp" ohos:center_in_parent="true" ohos:align_parent_bottom="true" ohos:bottom_margin="120vp"/> <Button ohos:id="$+id:choose_button" ohos:width="match_content" ohos:height="match_content" ohos:text="Choose Image" ohos:text_size="19fp" ohos:text_color="#FFFFFF" ohos:top_padding="8vp" ohos:bottom_padding="8vp" ohos:right_padding="70vp" ohos:left_padding="70vp" ohos:background_element="$graphic:background_button" ohos:center_in_parent="true" ohos:align_parent_bottom="true" ohos:bottom_margin="75vp"/> <Button ohos:id="$+id:button" ohos:width="match_content" ohos:height="match_content" ohos:text="Compress" ohos:text_size="19fp" ohos:text_color="#FFFFFF" ohos:top_padding="8vp" ohos:bottom_padding="8vp" ohos:right_padding="70vp" ohos:left_padding="70vp" ohos:background_element="$graphic:background_button" ohos:center_in_parent="true" ohos:align_parent_bottom="true" ohos:bottom_margin="15vp"/> </DependentLayout> 2.3. 图像压缩
核心类：Compressor
核心方法：
(1)自定义压缩：
public static File customCompress(Context context,鸿蒙 File file, int width, int height, int quality) throws IOException 参数：
context - 应用程序上下文
file - 待压缩图片抽象路径名
width - 压缩后宽度
height - 压缩后高度
quality - 图片压缩质量，范围0~100
结果：
返回压缩后图片抽象路径名。开件
异常：
发生I/O异常
(2)默认压缩：
public static File defaultCompress(Context context,鸿蒙 File file) throws IOException 参数：
context - 应用程序上下文
file - 待压缩图片抽象路径名
结果：
返回压缩后图片抽象路径名。
异常：
发生I/O异常
简单示例：
运行示例前需要在模拟器保存一张截图或使用相机功能照一张照片
public void onStart(Intent intent) { super.onStart(intent); super.setUIContent(ResourceTable.Layout_ability_main); // 请求文件的开件读取权限 String[] permissions = { "ohos.permission.READ_USER_STORAGE"}; requestPermissionsFromUser(permissions, 0); // 获取压缩按钮并绑定事件 Button button = (Button) findComponentById(ResourceTable.Id_button); if (button != null) { // 为按钮设置点击回调 button.setClickedListener(new Component.ClickedListener() { @Override public void onClick(Component component) { try { File file = new File(System.getProperty("java.io.tmpdir") + File.separator + tmpName); HiLog.error(LOG_LABEL, "old size..." + file.length() + " ...b"); // 默认压缩 // File newFile = Compressor.defaultCompress(file); // 自定义压缩 File newFile = Compressor.customCompress(getContext(), file, 500, 1000, 60); Text text = (Text) findComponentById(ResourceTable.Id_text); text.setText("size: " + newFile.length() + " b"); HiLog.error(LOG_LABEL, "new size..." + newFile.length() + " ...b"); PixelMap newPixelMap = Compressor.decode(newFile); Image image = (Image) findComponentById(ResourceTable.Id_image1); image.setPixelMap(newPixelMap); } catch (IOException e) { e.printStackTrace(); } } }); } // 获取选择图片按钮并绑定事件 Button chooseButton = (Button) findComponentById(ResourceTable.Id_choose_button); if (chooseButton != null) { // 为按钮设置点击回调 chooseButton.setClickedListener(new Component.ClickedListener() { @Override public void onClick(Component component) { DataAbilityHelper helper = DataAbilityHelper.creator(getContext()); try { ResultSet resultSet = helper.query(AVStorage.Images.Media.EXTERNAL_DATA_ABILITY_URI, null, null); while (resultSet != null && resultSet.goToNextRow()) { // 互殴媒体库的图片 int id = resultSet.getInt(resultSet.getColumnIndexForName(AVStorage.Images.Media.ID)); HiLog.error(LOG_LABEL, "id:..." + id + " ..."); Uri uri = Uri.appendEncodedPathToUri(AVStorage.Images.Media.EXTERNAL_DATA_ABILITY_URI, "" + id); // 根据图片的uri打开文件并保存到临时目录中 FileDescriptor fileDescriptor = helper.openFile(uri, "r"); ImageSource.DecodingOptions decodingOpts = new ImageSource.DecodingOptions(); decodingOpts.sampleSize = ImageSource.DecodingOptions.DEFAULT_SAMPLE_SIZE; ImageSource imageSource = ImageSource.create(fileDescriptor, null); PixelMap pixelMap = imageSource.createThumbnailPixelmap(decodingOpts, true); ImagePacker imagePacker = ImagePacker.create(); tmpName = UUID.randomUUID().toString(); File file = new File(System.getProperty("java.io.tmpdir") + File.separator + tmpName); FileOutputStream outputStream = new FileOutputStream(file); ImagePacker.PackingOptions packingOptions = new ImagePacker.PackingOptions(); packingOptions.quality = 100; boolean result = imagePacker.initializePacking(outputStream, packingOptions); result = imagePacker.addImage(pixelMap); long dataSize = imagePacker.finalizePacking(); // 显示图片和图片大小 Text text = (Text) findComponentById(ResourceTable.Id_text); text.setText("size: " + file.length() + " b"); Image image = (Image) findComponentById(ResourceTable.Id_image1); image.setPixelMap(pixelMap); } } catch (DataAbilityRemoteException | FileNotFoundException e) { e.printStackTrace(); } } }); } } 3. 组件compress开发实现
3.1. 拷贝图片制临时目录
传入的图片路径拷贝临时文件到应用的临时目录。香港云服务器
private static File copyToCache(Context context,鸿蒙 File imageFile) throws IOException { PixelMap pixelMap = decode(imageFile); String cachePath = context.getCacheDir() + File.separator + imageFile.getName(); File cacheFile = new File(cachePath); int quality = 100; // 压缩质量 refreshTmpFile(pixelMap, cacheFile, quality); return cacheFile; } 3.2. 图片解码
对临时目录里的图片进行解码
private static PixelMap decode(File file, int width, int height) { ImageSource imageSource = ImageSource.create(file, null); mageSource.DecodingOptions decodingOpts = new ImageSource.DecodingOptions(); decodingOpts.desiredSize = new Size(width, height); return imageSource.createPixelmap(decodingOpts); } 3.3. 图片编码
按照开发人员设定的规则进行编码，生成新图片
private static void refreshTmpFile(PixelMap pixelMap,开件 File file, int quality) throws IOException { ImagePacker imagePacker = ImagePacker.create(); ImagePacker.PackingOptions options = new ImagePacker.PackingOptions(); options.quality = quality; imagePacker.initializePacking(new FileOutputStream(file), options); imagePacker.addImage(pixelMap); imagePacker.finalizePacking(); } 项目源代码地址：https://github.com/isoftstone-dev/Compressor_Harmony
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想了解更多内容，请访问：
和华为官方合作共建的鸿蒙技术社区
https://harmonyos.51cto.com/#zz
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