如何在安卓系统中压缩图像文件？

Question

对于每个图像，我都有它的路径（以字符串形式）。然后我将该路径字符串转换为文件。然后将该文件存储到Firebase存储中，但我的问题是当我查询时该文件太大了。因此，在将其上传到Firebase存储之前，我需要对其进行压缩。我正在寻找解决方法，但从未找到一个清晰明确的解决方案。如果有人能帮助我提供非常清晰简单的解决方案，那就太好了。以下是我的代码。

for(String path : images)
{
    try {
    InputStream stream = new FileInputStream(new File(path));
    UploadTask uploadTask = imageStorage.putStream(stream);
    uploadTask.addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception exception) {
            // Handle unsuccessful uploads
            Log.d("myStorage","failure :(");
        }
    }).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
        @Override
        public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
            // taskSnapshot.getMetadata() contains file metadata such as size, content-type, and download URL.
            UrI downloadUrl = taskSnapshot.getDownloadUrl();
            Log.d("myStorage","success!");
        }
    });
    } catch (FileNotFoundException e) {
    e.printStackTrace();
    }
    countDB++;

}

- TheQ

---

你使用什么格式来存储图像在数据库中？如果可能的话，尝试使用BLOB格式来存储图像。这将自动将图像大小减小到KB。 - Priya Jagtap

我目前正在使用JPEG。 - TheQ

是的，但数据库中的格式是什么？是varchar还是int或blob等？ - Priya Jagtap

Answer 1

我有一个用于图像压缩的自定义类，我将其用于Firebase存储，并且大小显著减小。

这个类可以用于在发送到Firebase之前压缩位图和文件。

public class ImageCompression {

public static Bitmap getThumbnail(Uri uri, Context context) throws FileNotFoundException, IOException {
    InputStream input = context.getContentResolver().openInputStream(uri);

    BitmapFactory.Options onlyBoundsOptions = new BitmapFactory.Options();
    onlyBoundsOptions.inJustDecodeBounds = true;
    onlyBoundsOptions.inDither = true;//optional
    onlyBoundsOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;//optional
    BitmapFactory.decodeStream(input, null, onlyBoundsOptions);
    input.close();
    if ((onlyBoundsOptions.outWidth == -1) || (onlyBoundsOptions.outHeight == -1))
        return null;

    int originalSize = (onlyBoundsOptions.outHeight > onlyBoundsOptions.outWidth) ? onlyBoundsOptions.outHeight : onlyBoundsOptions.outWidth;

    double ratio = (originalSize > 500) ? (originalSize / 500) : 1.0;

    BitmapFactory.Options bitmapOptions = new BitmapFactory.Options();
    bitmapOptions.inSampleSize = getPowerOfTwoForSampleRatio(ratio);
    bitmapOptions.inDither = true;//optional
    bitmapOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;//optional
    input = context.getContentResolver().openInputStream(uri);
    Bitmap bitmap = BitmapFactory.decodeStream(input, null, bitmapOptions);
    input.close();
    return bitmap;
}

private static int getPowerOfTwoForSampleRatio(double ratio) {
    int k = Integer.highestOneBit((int) Math.floor(ratio));
    if (k == 0) return 1;
    else return k;
}

public static File compressFile(File file, Context context) {
    try {

        // BitmapFactory options to downsize the image
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        o.inSampleSize = 6;
        // factor of downsizing the image

        FileInputStream inputStream = new FileInputStream(file);
        //Bitmap selectedBitmap = null;
        BitmapFactory.decodeStream(inputStream, null, o);
        inputStream.close();

        // The new size we want to scale to
        final int REQUIRED_SIZE = 75;

        // Find the correct scale value. It should be the power of 2.
        int scale = 1;
        while (o.outWidth / scale / 2 >= REQUIRED_SIZE &&
                o.outHeight / scale / 2 >= REQUIRED_SIZE) {
            scale *= 2;
        }

        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        inputStream = new FileInputStream(file);

        Bitmap selectedBitmap = BitmapFactory.decodeStream(inputStream, null, o2);
        inputStream.close();

        // here i override the original image file
        file.createNewFile();
        FileOutputStream outputStream = new FileOutputStream(file);

        selectedBitmap.compress(Bitmap.CompressFormat.JPEG, 50, outputStream);

        return file;
    } catch (Exception e) {
        return null;
    }
}
} 



ImageCompression.compressFile(YourFile, this);
ImageCompression.getThumbnail(YourUri, this);

- Veeresh Charantimath

---

我应该用什么替换“MyApplication”？ - TheQ

那就是上下文，我使用应用程序上下文来实现这个。 - Veeresh Charantimath

MyApplication 仍然存在错误，我应该用什么替换它？ - TheQ

让我们在聊天中继续这个讨论。 - Veeresh Charantimath

非常棒的答案，感谢您提供详细的解决方案！ - Matan Dahan

Answer 2

这是你需要做的:

首先，将你的图片转换成位图:

Bitmap bitmap = ((BitmapDrawable) logo.getDrawable()).getBitmap();

将代码中的'logo'替换为您的imageView。然后，

byte[] byteImage = encodeToBase64(bitmap);

public static byte[] encodeToBase64(Bitmap image) {
    ByteArrayOutputStream byteArrayOS = new ByteArrayOutputStream();
    image.compress(Bitmap.CompressFormat.PNG, 25, byteArrayOS);
    byte[] byteArray = byteArrayOS.toByteArray();
    return byteArray;
}

你将把图像以字节形式存储在'byteImage'变量中。数字“25”表示你想要压缩的百分比。在这段代码中，它将图像大小减小到25%。尝试运行代码并让我知道结果 :)

- Abhi

---

是的，它能够减小文件大小。如果我想让图像特别是1024 x 1024，我该怎么做？ - TheQ

你想要在不降低图像分辨率的情况下减小文件大小吗？ - Abhi

@TheQ 我不确定这对你是否有效，但是尝试使用tinyPNG API，这是链接TinyPNG。 - Abhi

Answer 3

您可以使用以下代码获取所需大小的位图：

public static Bitmap decodeSampledBitmapFromArray(byte[] data, int reqWidth, int reqHeight) {
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeByteArray(data, 0, data.length, options);
    options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeByteArray(data, 0, data.length, options);
}

 public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;
    if (height > reqHeight || width > reqWidth) {

        final int halfHeight = height / 2;
        final int halfWidth = width / 2;

        // Calculate the largest inSampleSize value that is a power of 2 and keeps both
        // height and width larger than the requested height and width.
        while ((halfHeight / inSampleSize) >= reqHeight
                && (halfWidth / inSampleSize) >= reqWidth) {
            inSampleSize *= 2;
        }
    }
    return inSampleSize;
}

使用位图的字节数组和所需的宽度和高度调用decodeSampledBitmapFromArray。

以下是从位图获取字节数组的方法：

Bitmap bmp = Your_bitmap;
ByteArrayOutputStream stream = new ByteArrayOutputStream();
bmp.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

- Randheer

Answer 4

ImageView imageView = (ImageView)findViewById(R.id.imageView);
Bitmap bitmap = ImageUtils.getInstant().getCompressedBitmap("Your_Image_Path_Here");
imageView.setImageBitmap(bitmap);

ImageUtils.java:

public class ImageUtils {

    public static ImageUtils mInstant;

    public static ImageUtils getInstant(){
        if(mInstant==null){
            mInstant = new ImageUtils();
        }
        return mInstant;
    }

    public  Bitmap getCompressedBitmap(String imagePath) {
        float maxHeight = 1920.0f;
        float maxWidth = 1080.0f;
        Bitmap scaledBitmap = null;
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        Bitmap bmp = BitmapFactory.decodeFile(imagePath, options);

        int actualHeight = options.outHeight;
        int actualWidth = options.outWidth;
        float imgRatio = (float) actualWidth / (float) actualHeight;
        float maxRatio = maxWidth / maxHeight;

        if (actualHeight > maxHeight || actualWidth > maxWidth) {
            if (imgRatio < maxRatio) {
                imgRatio = maxHeight / actualHeight;
                actualWidth = (int) (imgRatio * actualWidth);
                actualHeight = (int) maxHeight;
            } else if (imgRatio > maxRatio) {
                imgRatio = maxWidth / actualWidth;
                actualHeight = (int) (imgRatio * actualHeight);
                actualWidth = (int) maxWidth;
            } else {
                actualHeight = (int) maxHeight;
                actualWidth = (int) maxWidth;

            }
        }

        options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);
        options.inJustDecodeBounds = false;
        options.inDither = false;
        options.inPurgeable = true;
        options.inInputShareable = true;
        options.inTempStorage = new byte[16 * 1024];

        try {
            bmp = BitmapFactory.decodeFile(imagePath, options);
        } catch (OutOfMemoryError exception) {
            exception.printStackTrace();

        }
        try {
            scaledBitmap = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.ARGB_8888);
        } catch (OutOfMemoryError exception) {
            exception.printStackTrace();
        }

        float ratioX = actualWidth / (float) options.outWidth;
        float ratioY = actualHeight / (float) options.outHeight;
        float middleX = actualWidth / 2.0f;
        float middleY = actualHeight / 2.0f;

        Matrix scaleMatrix = new Matrix();
        scaleMatrix.setScale(ratioX, ratioY, middleX, middleY);

        Canvas canvas = new Canvas(scaledBitmap);
        canvas.setMatrix(scaleMatrix);
        canvas.drawBitmap(bmp, middleX - bmp.getWidth() / 2, middleY - bmp.getHeight() / 2, new Paint(Paint.FILTER_BITMAP_FLAG));

        ExifInterface exif = null;
        try {
            exif = new ExifInterface(imagePath);
            int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, 0);
            Matrix matrix = new Matrix();
            if (orientation == 6) {
                matrix.postRotate(90);
            } else if (orientation == 3) {
                matrix.postRotate(180);
            } else if (orientation == 8) {
                matrix.postRotate(270);
            }
            scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);
        } catch (IOException e) {
            e.printStackTrace();
        }
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 85, out);

        byte[] byteArray = out.toByteArray();

        Bitmap updatedBitmap = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);

        return updatedBitmap;
    }

    private int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {
            final int heightRatio = Math.round((float) height / (float) reqHeight);
            final int widthRatio = Math.round((float) width / (float) reqWidth);
            inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
        }
        final float totalPixels = width * height;
        final float totalReqPixelsCap = reqWidth * reqHeight * 2;

        while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
            inSampleSize++;
        }
        return inSampleSize;
    }
}

这将压缩图像的大小，但不会改变其尺寸。

感谢这个答案在Android中压缩位图

- rana_sadam