从图库中选择图像到 ImageView 后的图像压缩

Question

我一直在搜索图像压缩，我发现这个有用的链接是类似whatsapp 的压缩示例http://grishma102.blogspot.ug/2016/03/image-compression-in-android.html，并在同一问题上阅读了不同的帖子，例如How whatsapp/Instagram or other compresses the image before uploading it to server?，但我未能实现我想要的。

我的成就是：-

1. 我希望当我从图库中选择一张图片时，它会在已压缩的情况下将其自身附加到 ImageView 上。

我就是这样做的

 @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);


    if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK) {
        if (data == null) {
            //showError("Failed to open picture!");
            return;
        }
        try {

            imageUri = data.getData();
            compressImage(imageUri.toString());
            Picasso.with(c).load(imageUri).fit().into(imageSelect);


        } catch (Exception e) {

            e.printStackTrace();
        }
    }
}

当然还有compressImage()方法，如下我从我发布的链接中得到的，

  public static String compressImage(String imagePath) {
    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.RGB_565);
    } 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));
    if (bmp != null) {
        bmp.recycle();
    }
    ExifInterface exif;
    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();
    }
    FileOutputStream out = null;
    String filepath = getFilename();
    try {
        //new File(imageFilePath).delete();
        out = new FileOutputStream(filepath);

        //write the compressed bitmap at the destination specified by filename.
        scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);

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

    return filepath;
}

public static String getFilename() {
    File mediaStorageDir = new File(Environment.getExternalStorageDirectory()
            + "/ImageCompApp/Images");

    // Create the storage directory if it does not exist
    if (!mediaStorageDir.exists()) {
        mediaStorageDir.mkdirs();
    }

    String mImageName = "IMG_" + String.valueOf(System.currentTimeMillis()) + ".jpg";
    String uriString = (mediaStorageDir.getAbsolutePath() + "/" + mImageName);
    return uriString;
}

public static void hideKeyboard(Activity context) {
    try {
        if (context == null) return;
        InputMethodManager imm = (InputMethodManager) context.getSystemService(Context.INPUT_METHOD_SERVICE);
        imm.hideSoftInputFromWindow(context.getWindow().getCurrentFocus().getWindowToken(), 0);
    } catch (Exception e) {
    }
}

但它并没有按照预期的方式工作，请问我哪里错了

Answer 1

试试这个代码：

 public String compressImage(String imageUri) {

        String filePath = getRealPathFromURI(imageUri);
        Bitmap scaledBitmap = null;

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

//      by setting this field as true, the actual bitmap pixels are not loaded in the memory. Just the bounds are loaded. If
//      you try the use the bitmap here, you will get null.
        options.inJustDecodeBounds = true;
        Bitmap bmp = BitmapFactory.decodeFile(filePath, options);

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

//      max Height and width values of the compressed image is taken as 816x612

        float maxHeight = 500.0f;
        float maxWidth = 500.0f;
        float imgRatio = actualWidth / actualHeight;
        float maxRatio = maxWidth / maxHeight;

//      width and height values are set maintaining the aspect ratio of the image

        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;

            }
        }

//      setting inSampleSize value allows to load a scaled down version of the original image

        options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);

//      inJustDecodeBounds set to false to load the actual bitmap
        options.inJustDecodeBounds = false;

//      this options allow android to claim the bitmap memory if it runs low on memory
        options.inPurgeable = true;
        options.inInputShareable = true;
        options.inTempStorage = new byte[16 * 1024];

        try {
//          load the bitmap from its path
            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));

//      check the rotation of the image and display it properly
        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 = getFilename();
        try {
            out = new FileOutputStream(filename);

//          write the compressed bitmap at the destination specified by filename.
            scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);

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

        return filename;

    }

    public String getFilename() {
        File file = new File(Environment.getExternalStorageDirectory().getPath(), "MyFolder/Images");
        if (!file.exists()) {
            file.mkdirs();
        }
        String uriSting = (file.getAbsolutePath() + "/" + System.currentTimeMillis() + ".jpg");
        return uriSting;

    }

    private String getRealPathFromURI(String contentURI) {
        Uri contentUri = Uri.parse(contentURI);
        Cursor cursor = 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;
    }

上面的代码用于在保持纵横比的情况下减小图像的大小。

source

希望对你有帮助..