用Java将base64字符串转换为图像 [英] Convert base64 string to Image in Java

问题描述

我有一张图片通过 JSON 字符串发送给我.我想将该字符串转换为我的 android 应用程序中的图像，然后显示该图像.

I have an image being sent to me through a JSON string. I want to convert that string into an image in my android app and then display that image.

JSON 字符串如下所示:

The JSON string looks like this:

"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAVI..."

注意:我用...截断了字符串

Note: I truncated the string with a ...

我有一个函数(我认为)将字符串转换为图像.我这样做对吗?

I've got a function that (I think) converts the string into an image. Am I doing this right?

public Bitmap ConvertToImage(String image){
    try{
        InputStream stream = new ByteArrayInputStream(image.getBytes());
        Bitmap bitmap = BitmapFactory.decodeStream(stream);                 
        return bitmap;  
    }
    catch (Exception e) {
        return null;            
    }
}

然后我尝试像这样在我的 android 活动中显示它

Then I try to display it on my android activity like this

String image = jsonObject.getString("barcode_img");         
Bitmap myBitmap = this.ConvertToImage(image);
ImageView cimg = (ImageView)findViewById(R.id.imageView1);

//Now try setting dynamic image
cimg.setImageBitmap(myBitmap);

但是，当我这样做时，什么也没有显示.我在 logcat 中没有收到任何错误.我做错了什么?

However, when I do this, nothing shows up. I don't get any errors in the logcat. What am I doing wrong?

谢谢

推荐答案

我担心你只需要解码 base64 字符串来获取图像字节，所以在你的

I'm worried about that you need to decode only the base64 string to get the image bytes, so in your

"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAVI..."

string，你必须得到data:image/png;base64,之后的数据，所以你只得到图像字节然后解码:

string, you must get the data after data:image/png;base64,, so you get only the image bytes and then decode them:

String imageDataBytes = completeImageData.substring(completeImageData.indexOf(",")+1);

InputStream stream = new ByteArrayInputStream(Base64.decode(imageDataBytes.getBytes(), Base64.DEFAULT));

这是一段代码，让您了解它的工作原理，但如果您收到一个 JSON 对象，则应该以正确方式完成:

This is a code so you understand how it works, but if you receive a JSON object it should be done the correct way:

• 将 JSON 字符串转换为 JSON 对象.
• 提取data键下的字符串.
• 确保以 image/png 开头，以便您知道是 png 图像.
• 确保包含 base64 字符串，以便您知道必须对数据进行解码.
• 解码base64字符串后的数据得到图像.

• Converting the JSON string to a JSON object.
• Extract the String under data key.
• Make sure that starts with image/png so you know is a png image.
• Make sure that contains base64 string, so you know that data must be decoded.
• Decode the data after base64 string to get the image.

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