HarmonyOS三方件開發指南（7）——compress組件

目錄：java

1. 組件compress功能介紹
1.1. 組件介紹：
compress是一個輕量級圖像壓縮庫。compress容許將大照片壓縮成小尺寸的照片，圖像質量損失很是小或能夠忽略不計。dom

1.2. 手機模擬器上運行效果：
ide

2. 組件compress使用方法
2.1. 添加依賴
將compress-debug.har複製到應用的entry\libs目錄下便可（因爲build.gradle中已經依賴的libs目錄下的*.har，所以不須要再作修改）。佈局

2.2. 設置佈局post

<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. 圖像壓縮
核心類：Compressorgradle

核心方法：ui

（1）自定義壓縮：

public static File customCompress(Context context, File file, int width, int height, int quality) throws IOException

參數：

context - 應用程序上下文

file - 待壓縮圖片抽象路徑名

width - 壓縮後寬度

height - 壓縮後高度

quality - 圖片壓縮質量，範圍0~100

結果：

返回壓縮後圖片抽象路徑名。

異常：

發生I/O異常

（2）默認壓縮：

public static File defaultCompress(Context context, File file) throws IOException

參數：

context - 應用程序上下文

file - 待壓縮圖片抽象路徑名

結果：

返回壓縮後圖片抽象路徑名。

異常：

發生I/O異常

簡單示例：

運行示例前須要在模擬器保存一張截圖或使用相機功能照一張照片

public void onStart(Intent intent) {

    super.onStart(intent);

    super.setUIContent(ResourceTable.Layout_ability_main);



    // 請求文件的讀取權限

    String[] permissions = {"ohos.permission.READ_USER_STORAGE"};

    requestPermissionsFromUser(permissions, 0);



    // 獲取壓縮按鈕並綁定事件

    Button button = (Button) findComponentById(ResourceTable.Id_button);

    if (button != null) {

        // 爲按鈕設置點擊回調

        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");



                    // 默認壓縮

                    // File newFile = Compressor.defaultCompress(file);



                    // 自定義壓縮

                    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();

                }

            }

        });

    }

    // 獲取選擇圖片按鈕並綁定事件

    Button chooseButton = (Button) findComponentById(ResourceTable.Id_choose_button);

    if (chooseButton != null) {

        // 爲按鈕設置點擊回調

        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()) {

                        // 互毆媒體庫的圖片

                        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);

                        // 根據圖片的uri打開文件並保存到臨時目錄中

                        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();

                        // 顯示圖片和圖片大小

                        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. 組件compress開發實現
3.1. 拷貝圖片制臨時目錄
傳入的圖片路徑拷貝臨時文件到應用的臨時目錄。

private static File copyToCache(Context context, File imageFile) throws IOException {

    PixelMap pixelMap = decode(imageFile);

    String cachePath = context.getCacheDir() + File.separator + imageFile.getName();

    File cacheFile = new File(cachePath);

    int quality = 100; // 壓縮質量

    refreshTmpFile(pixelMap, cacheFile, quality);

    return cacheFile;

}

3.2. 圖片解碼
對臨時目錄裏的圖片進行解碼

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. 圖片編碼
按照開發人員設定的規則進行編碼，生成新圖片

private static void refreshTmpFile(PixelMap pixelMap, 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();

}

項目源代碼地址：https://github.com/isoftstone-dev/Compressor_Harmony

做者：軟通田可輝

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