鸿蒙基于图像模块实现图库图片的四种常见操作开发分享

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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：

<?xml version="1.0" encoding="utf-8"?>  
<DirectionalLayout  
    xmlns:ohos="http://schemas.huawei.com/res/ohos"  
    ohos:height="match_parent"  
    ohos:width="match_parent"  
    ohos:orientation="vertical">  
  
    <Text  
        ohos:height="match_content"  
        ohos:width="match_content"  
        ohos:layout_alignment="horizontal_center"  
        ohos:text="HarmonyOS图像开发"  
        ohos:text_size="80"  
        ohos:top_margin="40vp"  
        />  
  
    <DirectionalLayout  
        xmlns:ohos="http://schemas.huawei.com/res/ohos"  
        ohos:height="match_content"  
        ohos:width="match_content"  
        ohos:layout_alignment="horizontal_center"  
        ohos:orientation="horizontal"  
        ohos:top_margin="20vp">  
  
        <Button  
            ohos:id="$+id:whirl_image"  
            ohos:height="match_content"  
            ohos:width="match_content"  
            ohos:background_element="$graphic:background_button"  
            ohos:padding="12vp"  
            ohos:right_margin="5vp"  
            ohos:text="旋转"  
            ohos:text_size="20vp"  
            ohos:top_margin="10vp">  
        </Button>  
  
        <Button  
            ohos:id="$+id:crop_image"  
            ohos:height="match_content"  
            ohos:width="match_content"  
            ohos:background_element="$graphic:background_button"  
            ohos:left_margin="5vp"  
            ohos:padding="12vp"  
            ohos:text="剪裁"  
            ohos:text_size="20vp"  
            ohos:top_margin="10vp">  
        </Button>  
  
        <Button  
            ohos:id="$+id:scale_image"  
            ohos:height="match_content"  
            ohos:width="match_content"  
            ohos:background_element="$graphic:background_button"  
            ohos:left_margin="5vp"  
            ohos:padding="12vp"  
            ohos:text="缩放"  
            ohos:text_size="20vp"  
            ohos:top_margin="10vp">  
        </Button>  
  
        <Button  
            ohos:id="$+id:mirror_image"  
            ohos:height="match_content"  
            ohos:width="match_content"  
            ohos:background_element="$graphic:background_button"  
            ohos:left_margin="5vp"  
            ohos:padding="12vp"  
            ohos:text="镜像"  
            ohos:text_size="20vp"  
            ohos:top_margin="10vp"/>  
    </DirectionalLayout>  
  
    <Image  
        ohos:id="$+id:image"  
        ohos:height="match_content"  
        ohos:width="match_content"  
        ohos:image_src="$media:shanghai.jpg"  
        ohos:layout_alignment="horizontal_center"  
        ohos:top_margin="20vp">  
    </Image>  
  
</DirectionalLayout> 

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

<?xml version="1.0" encoding="utf-8"?>  
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"  
       ohos:shape="rectangle">  
    <corners  
        ohos:radius="40"/>  
    <solid  
        ohos:color="#e9e9e9"/>  
</shape> 

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。

想了解更多内容，请访问：

51CTO和华为官方合作共建的鸿蒙技术社区

https://harmonyos.51cto.com