位图到 Base 64 编码字符串答案

【问题标题】：Bitmap to Base 64 Encode String位图到 Base 64 编码字符串
【发布时间】：2023-03-26 05:39:01
【问题描述】：

我正在尝试将图像转换为位图，然后将其编码为 base64 字符串。我在行上遇到空指针异常

 bMap.compress(Bitmap.CompressFormat.PNG, COMPRESSION_QUALITY,
            byteArrayBitmapStream);

怎么了？请注意，我将带有图片“pic2.jpg”的文件名输入到下面的方法中。

下面是我的代码：

    private String convertToBitmap (String name){
    File imgFile = new File (name);
    Bitmap bMap = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
    final int COMPRESSION_QUALITY = 100;
    String encodedImage;
    ByteArrayOutputStream byteArrayBitmapStream = new ByteArrayOutputStream();
    bMap.compress(Bitmap.CompressFormat.PNG, COMPRESSION_QUALITY,
            byteArrayBitmapStream);
    byte[] b = byteArrayBitmapStream.toByteArray();
    encodedImage = Base64.encodeToString(b, Base64.DEFAULT);
    return encodedImage;
}

在我的日志猫下面：

03-22 23:03:44.916 18331-18331/? I/art: Not late-enabling -Xcheck:jni (already on)
03-22 23:03:44.916 18331-18331/? W/art: Unexpected CPU variant for X86 using defaults: x86
03-22 23:03:45.029 18331-18331/com.example.reynaldo.getimageserver W/System: ClassLoader referenced unknown path: /data/app/com.example.reynaldo.getimageserver-2/lib/x86
03-22 23:03:45.038 18331-18331/com.example.reynaldo.getimageserver I/InstantRun: Instant Run Runtime started. Android package is com.example.reynaldo.getimageserver, real application class is null.
03-22 23:03:45.124 18331-18331/com.example.reynaldo.getimageserver W/System: ClassLoader referenced unknown path: /data/app/com.example.reynaldo.getimageserver-2/lib/x86
03-22 23:03:45.372 18331-18331/com.example.reynaldo.getimageserver W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
03-22 23:03:45.676 18331-18361/com.example.reynaldo.getimageserver D/NetworkSecurityConfig: No Network Security Config specified, using platform default
03-22 23:03:45.865 18331-18367/com.example.reynaldo.getimageserver I/OpenGLRenderer: Initialized EGL, version 1.4
03-22 23:03:45.865 18331-18367/com.example.reynaldo.getimageserver D/OpenGLRenderer: Swap behavior 1
03-22 23:03:45.908 18331-18367/com.example.reynaldo.getimageserver E/EGL_emulation: tid 18367: eglSurfaceAttrib(1174): error 0x3009 (EGL_BAD_MATCH)
03-22 23:03:45.909 18331-18367/com.example.reynaldo.getimageserver W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xb493fe00, error=EGL_BAD_MATCH

【问题讨论】：

I'm getting a null pointer exception on the line 你的意思是bMap 是空的吗？
我相信是的，我认为我使用的文件路径不正确。但是我从终端得到了文件路径，放到方法里面还是不行。
可能文件太大了。检查这个答案：stackoverflow.com/a/8442683/5241603
我已将日志猫添加到帖子中
@Geek96 是的，一定要确定路径，因为如果指定的文件名是空的，或者不能解码成位图，函数返回空，检查docs。使用try catch 并打印日志

标签： android image encoding bitmap

【解决方案1】：

试试这个

    Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image); // your pic2
    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
    byte[] bitmapdata = stream.toByteArray();
    encodedImage = Base64.encodeToString(bitmapdata, Base64.DEFAULT);
    return encodedImage;

【讨论】：

【解决方案2】：

Bitmap bitmap = optimizePhoto();
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOutputStream);
byte[] byteArray = byteArrayOutputStream.toByteArray();
Strng encoded = Base64.encodeToString(byteArray, Base64.DEFAULT);

如果您需要进一步优化图像

private Bitmap optimizePhoto() {
        // Get the dimensions of the View
        int targetW = 300;
        int targetH = 300;

        // Get the dimensions of the bitmap
        BitmapFactory.Options bmOptions = new BitmapFactory.Options();
        bmOptions.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(getArguments().getString("imagePath"), bmOptions);
        int photoW = bmOptions.outWidth;
        int photoH = bmOptions.outHeight;

        // Determine how much to scale down the image
        int scaleFactor = Math.min(photoW / targetW, photoH / targetH);

        // Decode the image file into a Bitmap sized to fill the View
        bmOptions.inJustDecodeBounds = false;
        bmOptions.inSampleSize = scaleFactor;
        bmOptions.inPurgeable = true;

        Bitmap bitmap = BitmapFactory.decodeFile(getArguments().getString("imagePath"), bmOptions);

        return bitmap;
    }

【讨论】：

【解决方案3】：

你应该试试这个：

 private String convertToBitmap (String name){
            File imgFile = new File (name);
            Bitmap bMap = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
             if (bMap != null) {
                     bMap = Bitmap.createScaledBitmap(bMap, 256, 256, true);
            String encodedImage;
            ByteArrayOutputStream byteArrayBitmapStream = new ByteArrayOutputStream();
           bm.compress(Bitmap.CompressFormat.JPEG, 100, byteArrayBitmapStream);
            byte[] b = byteArrayBitmapStream.toByteArray();
            encodedImage = Base64.encodeToString(b, Base64.DEFAULT);
            StringBuilder sb = new StringBuilder();

            sb.append(encodedImage);
            encodeString = sb.toString();
            return encodedImage;
        }
}

【讨论】：