Android：如何减少所选文件的大小

在我们的android应用程序中，我们需要从galary和camera上传文件，这些文件的大小可能取决于te手机，在某些设备中可能超过2mb，因此我需要将文件大小减小到100kb以下，这样可以方便地保存在数据库中并修复OutOfMemory错误。减小文件大小的最佳方法是什么？我在watsapp中看到，当我们上传一个超过6mb的图像时，它将减少到大约50kb。这是怎么发生的。是通过找到最佳的inSampleSize，然后使用该类对文件进行解码吗？

使用该类压缩文件大小

public class CompressImage {

Context mContext;

public CompressImage(Context context) {
    this.mContext = context;
}

public String compressImage(String imageUri) throws IOException {

    String filePath = getRealPathFromURI(imageUri);
    if (filePath == null) {
        filePath = imageUri;
    }
    Bitmap scaledBitmap = null;

    BitmapFactory.Options options = new BitmapFactory.Options();

    options.inJustDecodeBounds = true;
    Bitmap bmp = BitmapFactory.decodeFile(filePath, options);

    int actualHeight = options.outHeight;
    int actualWidth = options.outWidth;


    float maxHeight = 816.0f;
    float maxWidth = 612.0f;
    float imgRatio = actualWidth / 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.inPurgeable = true;
    options.inInputShareable = true;
    options.inTempStorage = new byte[16 * 1024];

    try {
        bmp = BitmapFactory.decodeFile(filePath, 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;
    try {
        exif = new ExifInterface(filePath);

        int orientation = exif.getAttributeInt(
                ExifInterface.TAG_ORIENTATION, 0);
        Log.d("EXIF", "Exif: " + orientation);
        Matrix matrix = new Matrix();
        if (orientation == 6) {
            matrix.postRotate(90);
            Log.d("EXIF", "Exif: " + orientation);
        } else if (orientation == 3) {
            matrix.postRotate(180);
            Log.d("EXIF", "Exif: " + orientation);
        } else if (orientation == 8) {
            matrix.postRotate(270);
            Log.d("EXIF", "Exif: " + orientation);
        }
        scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0,
                scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix,
                true);
    } catch (IOException e) {
        e.printStackTrace();
    }

    FileOutputStream out = null;
    String filename = imageUri;
    File oldfile = new File(imageUri);
    if (oldfile.exists()) {
        oldfile.delete();
    }
    try {
        out = new FileOutputStream(filename);

        scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

    return filename;

}

public String getFilename() throws IOException {

    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
            .format(new Date());
    String imageFileName = "twice_" + timeStamp + "_";
    File storageDir = Environment
            .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
    File image = File.createTempFile(imageFileName, /* prefix */
            ".jpg", /* suffix */
            storageDir /* directory */
    );

    return image.getAbsolutePath();

}

private String getRealPathFromURI(String contentURI) {
    Uri contentUri = Uri.parse(contentURI);
    Cursor cursor = mContext.getContentResolver().query(contentUri, null, null, null, null);
    if (cursor == null) {
        return contentUri.getPath();
    } else {
        cursor.moveToFirst();
        int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
        return cursor.getString(index);
    }
}

public 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;
}

---

}

使用此类压缩文件大小

public class CompressImage {

Context mContext;

public CompressImage(Context context) {
    this.mContext = context;
}

public String compressImage(String imageUri) throws IOException {

    String filePath = getRealPathFromURI(imageUri);
    if (filePath == null) {
        filePath = imageUri;
    }
    Bitmap scaledBitmap = null;

    BitmapFactory.Options options = new BitmapFactory.Options();

    options.inJustDecodeBounds = true;
    Bitmap bmp = BitmapFactory.decodeFile(filePath, options);

    int actualHeight = options.outHeight;
    int actualWidth = options.outWidth;


    float maxHeight = 816.0f;
    float maxWidth = 612.0f;
    float imgRatio = actualWidth / 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.inPurgeable = true;
    options.inInputShareable = true;
    options.inTempStorage = new byte[16 * 1024];

    try {
        bmp = BitmapFactory.decodeFile(filePath, 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;
    try {
        exif = new ExifInterface(filePath);

        int orientation = exif.getAttributeInt(
                ExifInterface.TAG_ORIENTATION, 0);
        Log.d("EXIF", "Exif: " + orientation);
        Matrix matrix = new Matrix();
        if (orientation == 6) {
            matrix.postRotate(90);
            Log.d("EXIF", "Exif: " + orientation);
        } else if (orientation == 3) {
            matrix.postRotate(180);
            Log.d("EXIF", "Exif: " + orientation);
        } else if (orientation == 8) {
            matrix.postRotate(270);
            Log.d("EXIF", "Exif: " + orientation);
        }
        scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0,
                scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix,
                true);
    } catch (IOException e) {
        e.printStackTrace();
    }

    FileOutputStream out = null;
    String filename = imageUri;
    File oldfile = new File(imageUri);
    if (oldfile.exists()) {
        oldfile.delete();
    }
    try {
        out = new FileOutputStream(filename);

        scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

    return filename;

}

public String getFilename() throws IOException {

    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss")
            .format(new Date());
    String imageFileName = "twice_" + timeStamp + "_";
    File storageDir = Environment
            .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
    File image = File.createTempFile(imageFileName, /* prefix */
            ".jpg", /* suffix */
            storageDir /* directory */
    );

    return image.getAbsolutePath();

}

private String getRealPathFromURI(String contentURI) {
    Uri contentUri = Uri.parse(contentURI);
    Cursor cursor = mContext.getContentResolver().query(contentUri, null, null, null, null);
    if (cursor == null) {
        return contentUri.getPath();
    } else {
        cursor.moveToFirst();
        int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
        return cursor.getString(index);
    }
}

public 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;
}

---

}

您可以使用Glide来完成这项工作。这里有一个例子，不是fitCenter保持图像的比例

Glide.with(getContext())
                    .load(image)
                    .asBitmap()
                    .override(600,200)
                    .fitCenter()
                    .into(new SimpleTarget<Bitmap>() {
                @Override
                public void onResourceReady(Bitmap resource, GlideAnimation<? super Bitmap> glideAnimation) {
                    Log.i("MainActivity", "Bitmap Dimen : " + resource.getWidth()); // Excepting 105 but returns 300
                    // Store image to database
                }
            });

---

你可以用Glide做那项工作。这里有一个例子，不是fitCenter保持图像的比例

Glide.with(getContext())
                    .load(image)
                    .asBitmap()
                    .override(600,200)
                    .fitCenter()
                    .into(new SimpleTarget<Bitmap>() {
                @Override
                public void onResourceReady(Bitmap resource, GlideAnimation<? super Bitmap> glideAnimation) {
                    Log.i("MainActivity", "Bitmap Dimen : " + resource.getWidth()); // Excepting 105 but returns 300
                    // Store image to database
                }
            });

---

您可以缩小图像以缩小尺寸。@SalmanKhakwani如何做到？此方法的可能重复：您可以缩小图像以缩小尺寸。@SalmanKhakwani如何做到？此方法的可能重复：调整大小是否花费了很长时间？这也是最好的方法吗？它非常简单、最快，而且只需要图像大小减小，图像质量将保持不变。试试看！看起来和这里一样，是吗？调整大小花了很长时间吗？这也是最好的方法吗？它非常简单和最快的方法，只有图像大小减小图像质量才会相同。试试看！看起来和这里一样，是吗？？