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
<DirectionalLayout
xmlns:ohos="http://schemas.huawei.com/res/ohos"
ohos:height="match_parent"
ohos:width="match_parent"
ohos:orientation="vertical">
<Text
ohos:height="100vp"
ohos:width="match_parent"
ohos:background_element="#ffffff"
ohos:text="图片编码"
ohos:text_size="20vp"
ohos:text_alignment="center"
ohos:id="$+id:textRead"/>
<Text
ohos:id="$+id:getmPixelMapAndShowImage"
ohos:height="100vp"
ohos:width="match_parent"
ohos:text="图片解码并显示"
ohos:background_element="#ed6262"
ohos:text_size="20vp"
ohos:text_alignment="center"/>
<Image
ohos:height="match_parent"
ohos:width="match_parent"
ohos:id="$+id:ShowImage"/>
</DirectionalLayout>
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() {
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() {
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;
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() {
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() {
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