图库四种常见操作的HarmonyOS图像编解码开发

1. 项目介绍

HarmonyOS图像模块支持图像业务的开发，常见功能如图像解码、图像编码、基本的位图操作、图像编辑等。当然，也支持通过接口组合来实现更复杂的图像处理逻辑。本教程以图库图片中旋转、剪裁、缩放、镜像四种常见操作为例，给大家介绍HarmonyOS图像编解码的相关开发指导。

2. 将图片转换为PixelMap

图像解码就是将所支持格式的存档图片解码成统一的PixelMap图像，用于后续图像显示或其他处理，比如旋转、缩放、剪裁等。当前支持格式包括JPEG、PNG、GIF、HEIF、WebP、BMP。本例为您提供了getPixelMapFromResource函数，可以将resources/base/media目录下的图片资源转换为PixelMap图像，其中入参为图片的资源ID。

private PixelMap getPixelMapFromResource(int resourceId) {

    InputStream inputStream = null;
    try {
        // 创建图像数据源ImageSource对象
        inputStream = getContext().getResourceManager().getResource(resourceId);
        ImageSource.SourceOptions srcOpts = new ImageSource.SourceOptions();
        srcOpts.formatHint = "image/jpg";
        ImageSource imageSource = ImageSource.create(inputStream, srcOpts);


        // 设置图片参数
        ImageSource.DecodingOptions decodingOptions = new ImageSource.DecodingOptions();
        return imageSource.createPixelmap(decodingOptions);
    } catch (IOException e) {
        HiLog.info(LABEL_LOG, "IOException");
    } catch (NotExistException e) {
        HiLog.info(LABEL_LOG, "NotExistException");
    } finally {
        if (inputStream != null) {
            try {
                inputStream.close();
            } catch (IOException e) {
                HiLog.info(LABEL_LOG, "inputStream IOException");
            }
        }
    }
    return null;
}

3. 图片参数设置

本例使用图片像素的尺寸为1024*768，点击一次旋转按钮会进行90度的旋转，缩放是按照2：1的比例进行缩放，剪裁是保证宽度不变的情况下对高度进行400像素的剪裁，相关参数设置如下所示：

// 设置图片参数 
ImageSource.DecodingOptions decodingOptions = new ImageSource.DecodingOptions(); 
// 旋转 
decodingOptions.rotateDegrees = 90 * whirlCount; 
// 缩放 
decodingOptions.desiredSize = new Size(isScale ? 512 : 0, isScale ? 384 : 0); 
// 剪裁 
decodingOptions.desiredRegion = new Rect(0, 0, isCorp ? 1024 : 0, isCorp ? 400 : 0);

4. 图片镜像操作

图片镜像操作就是对图片以纵坐标为轴制作对称图片。image绘制的时候会调用onDraw方法，本例采用对图像Canvas画布的镜像操作实现图片的镜像显示，示例代码如下所示：

private void mirrorImage(PixelMap pixelMap) { 
    scaleX = -scaleX; 
    image.addDrawTask( 
            new Component.DrawTask() { 
                @Override 
                public void onDraw(Component component, Canvas canvas) { 
                    if (isMirror) { 
                        isMirror = false; 
                        PixelMapHolder pmh = new PixelMapHolder(pixelMap); 
                        canvas.scale( 
                                scaleX, 
                                1.0f, 
                                (float) pixelMap.getImageInfo().size.width / 2, 
                                (float) pixelMap.getImageInfo().size.height / 2); 
                        canvas.drawPixelMapHolder( 
                                pmh, 
                                0, 
                                0, 
                                new Paint()); 
                    } 
                } 
            }); 
}

5. 完整示例

以手机为例，初始化页面如图1所示，依次点击按钮可以实现图片的旋转、剪裁、缩放、镜像，效果如下所示（您需要准备一张像素尺寸为1024*768的图片，放到ImageDemo\entry\src\main\resources\base\media目录下）：

示例代码如下：

import com.huawei.codelab.ResourceTable; 
 
import ohos.aafwk.ability.AbilitySlice; 
import ohos.aafwk.content.Intent; 
import ohos.agp.components.Button; 
import ohos.agp.components.Component; 
import ohos.agp.components.Image; 
import ohos.agp.render.Canvas; 
import ohos.agp.render.Paint; 
import ohos.agp.render.PixelMapHolder; 
import ohos.global.resource.NotExistException; 
import ohos.hiviewdfx.HiLog; 
import ohos.hiviewdfx.HiLogLabel; 
import ohos.media.image.ImageSource; 
import ohos.media.image.PixelMap; 
import ohos.media.image.common.PixelFormat; 
import ohos.media.image.common.Rect; 
import ohos.media.image.common.Size; 
 
import java.io.IOException; 
import java.io.InputStream; 
 
/** 
 * 图像主页面 
 */ 
public class MainAbilitySlice extends AbilitySlice { 
    private static final HiLogLabel LABEL_LOG = new HiLogLabel(3, 0xD001100, "MainAbilitySlice"); 
    Image image; 
    PixelMap imagePixelMap; 
    Button whirlImageBtn; 
    Button cropImageBtn; 
    Button scaleImageBtn; 
    Button mirrorImageBtn; 
    private int whirlCount = 0; 
    private boolean isCorp = false; 
    private boolean isScale = false; 
    private boolean isMirror = false; 
    private float scaleX = 1.0f; 
 
    @Override 
    public void onStart(Intent intent) { 
        super.onStart(intent); 
        super.setUIContent(ResourceTable.Layout_ability_main); 
        initView(); 
    } 
 
    private void initView() { 
        if (findComponentById(ResourceTable.Id_whirl_image) instanceof Button) { 
            whirlImageBtn = (Button) findComponentById(ResourceTable.Id_whirl_image); 
        } 
        if (findComponentById(ResourceTable.Id_crop_image) instanceof Button) { 
            cropImageBtn = (Button) findComponentById(ResourceTable.Id_crop_image); 
        } 
        if (findComponentById(ResourceTable.Id_scale_image) instanceof Button) { 
            scaleImageBtn = (Button) findComponentById(ResourceTable.Id_scale_image); 
        } 
        if (findComponentById(ResourceTable.Id_mirror_image) instanceof Button) { 
            mirrorImageBtn = (Button) findComponentById(ResourceTable.Id_mirror_image); 
        } 
        if (findComponentById(ResourceTable.Id_image) instanceof Image) { 
            image = (Image) findComponentById(ResourceTable.Id_image); 
        } 
        whirlImageBtn.setClickedListener(new ButtonClick()); 
        cropImageBtn.setClickedListener(new ButtonClick()); 
        scaleImageBtn.setClickedListener(new ButtonClick()); 
        mirrorImageBtn.setClickedListener(new ButtonClick()); 
    } 
 
    private class ButtonClick implements Component.ClickedListener { 
        @Override 
        public void onClick(Component component) { 
            int btnId = component.getId(); 
            switch (btnId) { 
                case ResourceTable.Id_whirl_image: 
                    // 旋转图片 
                    whirlCount++; 
                    isCorp = false; 
                    isScale = false; 
                    isMirror = false; 
                    imagePixelMap = getPixelMapFromResource(ResourceTable.Media_shanghai); 
                    image.setPixelMap(imagePixelMap); 
                    break; 
                case ResourceTable.Id_crop_image: 
                    // 剪裁图片 
                    whirlCount = 0; 
                    isCorp = !isCorp; 
                    isScale = false; 
                    isMirror = false; 
                    imagePixelMap = getPixelMapFromResource(ResourceTable.Media_shanghai); 
                    image.setPixelMap(imagePixelMap); 
                    break; 
                case ResourceTable.Id_scale_image: 
                    // 缩放图片 
                    whirlCount = 0; 
                    isCorp = false; 
                    isScale = !isScale; 
                    isMirror = false; 
                    imagePixelMap = getPixelMapFromResource(ResourceTable.Media_shanghai); 
                    image.setPixelMap(imagePixelMap); 
                    break; 
                case ResourceTable.Id_mirror_image: 
                    // 镜像图片 
                    whirlCount = 0; 
                    isCorp = false; 
                    isScale = false; 
                    isMirror = true; 
                    imagePixelMap = getPixelMapFromResource(ResourceTable.Media_shanghai); 
                    mirrorImage(imagePixelMap); 
                    image.setPixelMap(imagePixelMap); 
                    break; 
                default: 
                    break; 
            } 
        } 
    } 
 
    private void mirrorImage(PixelMap pixelMap) { 
        scaleX = -scaleX; 
        image.addDrawTask( 
                new Component.DrawTask() { 
                    @Override 
                    public void onDraw(Component component, Canvas canvas) { 
                        if (isMirror) { 
                            isMirror = false; 
                            PixelMapHolder pmh = new PixelMapHolder(pixelMap); 
                            canvas.scale( 
                                    scaleX, 
                                    1.0f, 
                                    (float) pixelMap.getImageInfo().size.width / 2, 
                                    (float) pixelMap.getImageInfo().size.height / 2); 
                            canvas.drawPixelMapHolder( 
                                    pmh, 
                                    0, 
                                    0, 
                                    new Paint()); 
                        } 
                    } 
                }); 
    } 
 
    /** 
     * 通过图片ID返回PixelMap 
     * 
     * @param resourceId 图片的资源ID 
     * @return 图片的PixelMap 
     */ 
    private PixelMap getPixelMapFromResource(int resourceId) { 
        InputStream inputStream = null; 
        try { 
            // 创建图像数据源ImageSource对象 
            inputStream = getContext().getResourceManager().getResource(resourceId); 
            ImageSource.SourceOptions srcOpts = new ImageSource.SourceOptions(); 
            srcOpts.formatHint = "image/jpg"; 
            ImageSource imageSource = ImageSource.create(inputStream, srcOpts); 
 
            // 设置图片参数 
            ImageSource.DecodingOptions decodingOptions = new ImageSource.DecodingOptions(); 
            // 旋转 
            decodingOptions.rotateDegrees = 90 * whirlCount; 
            // 缩放 
            decodingOptions.desiredSize = new Size(isScale ? 512 : 0, isScale ? 384 : 0); 
            // 剪裁 
            decodingOptions.desiredRegion = new Rect(0, 0, isCorp ? 1024 : 0, isCorp ? 400 : 0); 
            decodingOptions.desiredPixelFormat = PixelFormat.ARGB_8888; 
            return imageSource.createPixelmap(decodingOptions); 
        } catch (IOException e) { 
            HiLog.info(LABEL_LOG, "IOException"); 
        } catch (NotExistException e) { 
            HiLog.info(LABEL_LOG, "NotExistException"); 
        } finally { 
            if (inputStream != null) { 
                try { 
                    inputStream.close(); 
                } catch (IOException e) { 
                    HiLog.info(LABEL_LOG, "inputStream IOException"); 
                } 
            } 
        } 
        return null; 
    } 
 
    @Override 
    public void onActive() { 
        super.onActive(); 
    } 
 
    @Override 
    public void onForeground(Intent intent) { 
        super.onForeground(intent); 
    } 
} 

布局代码如下：

此外您还需在resource/base/graphic目录下添加background_button.xml

说明

以上代码仅demo演示参考使用，产品化的代码需要考虑数据校验和国际化。

编辑：hfy