Question

我正在将图片上传到服务器。我希望将图像大小减小到200KB。如何在android中做到这一点。

Answer 1

您可以使用Bitmap.compress()方法执行此操作。下面是一个示例代码，展示了如何实现相同的目标：

将图像缩放为宽高比的代码：

Bitmap bitmapImage = BitmapFactory.decodeFile("Your path");
int nh = (int) ( bitmapImage.getHeight() * (512.0 / bitmapImage.getWidth()) );
Bitmap scaled = Bitmap.createScaledBitmap(bitmapImage, 512, nh, true);
your_imageview.setImageBitmap(scaled);

压缩图像而不会像在Whatsapp中那样丢失质量：

    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 = 816.0f;
        float maxWidth = 612.0f;
        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;
    }

另外，也请检查this one。并且refer this还有一个用于服务器上传，希望它有所帮助！

Android如何在不失去质量的情况下缩小图像大小

1 个答案: