在HarmonyOS中对图片的解码和编码是常见的操作，在HarmonyOS怎么进行编码和解码呢？今天写一个demo进行实现该功能实现，我们从以下几个步骤进行讲解该功能

1.       准备环节

2.       图片编码为Base64字符串

3.       Base64解码为PixelMap，并显示在Image控件上

第一步准备环节

1.1    准备一张图片放在resources/rawfile文件夹下，图片如下

1.2 新建ImageAbilitySlice java类和xml布局， xml布局如下

XML效果图如下

第二步图片编码为Base64字符串

2.1这边我们参考资料是Base64的基本用法，来写一个工具类，代码如下

package com.harmony.alliance.mydemo.utils; import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.util.Base64; public class ImageUtils {     /**     * 将图片转换成Base64编码的字符串     */    public static String imageToBase64(String path){ if(path==null||path.equals("")){     return null; } InputStream is = null; byte[] data = null; String result = null; try{     is = new FileInputStream(path);     //创建一个字符流大小的数组。     data = new byte[is.available()];     //写入数组     is.read(data);     //用默认的编码格式进行编码     result = Base64.getEncoder().encodeToString(data); }catch (Exception e){     e.printStackTrace(); }finally {     if(null !=is){  try {      is.close();  } catch (IOException e) {      e.printStackTrace();  }     }  } return result;    }/**     * 将图片转换成Base64编码的字符串     */    public static String imageInputStreamToBase64(  InputStream is){ if(is==null){     return null; } byte[] data = null; String result = null; try{     //创建一个字符流大小的数组。     data = new byte[is.available()];     //写入数组     is.read(data);     //用默认的编码格式进行编码     result = Base64.getEncoder().encodeToString(data); }catch (Exception e){     e.printStackTrace(); }finally {     if(null !=is){  try {      is.close();  } catch (IOException e) {      e.printStackTrace();  }     }  } return result;    } }

2.2实现图片编码的代码如下

  textRead.setClickedListener(new Component.ClickedListener() {     @Override     public void onClick(Component component) {  try {      String filePath = String.format(Locale.ROOT, "assets/entry/resources/rawfile/%s", "icon.png");      InputStream is = this.getClass().getClassLoader().getResourceAsStream(filePath);      //Todo 得到base64字符串      ImageData="data:image/png;base64,"+ImageUtils.imageInputStreamToBase64(is);      HiLogUtils.PrintLog(ImageData);  }catch (Exception e){      e.printStackTrace();  }      } });

效果图如下

第三步将Base64解码为mPixelMap并显示在Image控件上

3.1我们这里使用如下Base64.getDecoder().decode和ImageSource、SourceOptions的相关技术，代码如下

   findComponentById(ResourceTable.Id_getmPixelMapAndShowImage).setClickedListener(new Component.ClickedListener() {     @Override     public void onClick(Component component) {  String Base64Data=  ImageData.replace("data:image/png;base64,","");  //todo base64字符串得到字节  byte[] base64byte=     java.util.Base64.getDecoder().decode(Base64Data);  ImageSource.SourceOptions srcOpts = new ImageSource.SourceOptions();  srcOpts.formatHint = "image/png";  ImageSource imageSource = ImageSource.create(base64byte, srcOpts);  // 设置图片参数  ImageSource.DecodingOptions decodingOptions = new ImageSource.DecodingOptions();  PixelMap mPixelMap =      imageSource.createPixelmap(decodingOptions);  ShowImage.setPixelMap(mPixelMap);     } });

效果图如下

整体代码如下

package com.harmony.alliance.mydemo.slice; import com.harmony.alliance.mydemo.ResourceTable;import com.harmony.alliance.mydemo.utils.ImageUtils;import ohos.aafwk.ability.AbilitySlice;import ohos.aafwk.content.Intent;import ohos.agp.components.Component;import ohos.agp.components.Image;import ohos.agp.components.Text;import ohos.global.resource.RawFileEntry;import ohos.global.resource.Resource;import ohos.media.image.ImageSource;import ohos.media.image.PixelMap; import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.util.Base64;import java.util.Locale; public class ImageAbilitySlice  extends AbilitySlice {    Image ShowImage;    private   String ImageData;    @Override    protected void onStart(Intent intent) { super.onStart(intent); setUIContent(ResourceTable.Layout_iamge_ability_slice); Text textRead= (Text) findComponentById(ResourceTable.Id_textRead); ShowImage= (Image) findComponentById(ResourceTable.Id_ShowImage); textRead.setClickedListener(new Component.ClickedListener() {     @Override     public void onClick(Component component) {  try {      String filePath = String.format(Locale.ROOT, "assets/entry/resources/rawfile/%s", "icon.png");      InputStream is = this.getClass().getClassLoader().getResourceAsStream(filePath);      //Todo 得到base64字符串      ImageData="data:image/png;base64,"+ImageUtils.imageInputStreamToBase64(is);      HiLogUtils.PrintLog(ImageData);  }catch (Exception e){      e.printStackTrace();  }      } });   findComponentById(ResourceTable.Id_getmPixelMapAndShowImage).setClickedListener(new Component.ClickedListener() {     @Override     public void onClick(Component component) {  String Base64Data=  ImageData.replace("data:image/png;base64,","");  //todo base64字符串得到字节  byte[] base64byte=     java.util.Base64.getDecoder().decode(Base64Data);  ImageSource.SourceOptions srcOpts = new ImageSource.SourceOptions();  srcOpts.formatHint = "image/png";  ImageSource imageSource = ImageSource.create(base64byte, srcOpts);  // 设置图片参数  ImageSource.DecodingOptions decodingOptions = new ImageSource.DecodingOptions();  PixelMap mPixelMap =      imageSource.createPixelmap(decodingOptions);  ShowImage.setPixelMap(mPixelMap);     } });      }  }

效果如下

更多相关学习资料：
https://developer.huawei.com/consumer/cn/forum/topic/0202768644032900242?fid=0102683795438680754?ha_source=zzh

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