上传图片时如何压缩文件大小和质量？

Question

上传图片时如何压缩文件大小和质量？

我已经完成了上传文件到firebase，如何压缩文件？

因为文件很大时，在recyclerview中加载会变慢。

所以我想压缩文件。

 Uri imageUri = imageListUri.get(index);
        if(spinner.getSelectedItem().toString().equals(getApplicationContext().getResources().getString(R.string.choose_sub))) {
            AlertDialog alertDialog = new AlertDialog.Builder(this)
                    .setTitle(getApplicationContext().getResources().getString(R.string.alert_error))
                    .setMessage(getApplicationContext().getResources().getString(R.string.choose_sub))
                    .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.dismiss();
                        }
                    }).create();
            alertDialog.show();
        } else if(image_check.equals("ok")) {
            final ProgressDialog progressDialog = new ProgressDialog(this);
            progressDialog.setMessage(getApplicationContext().getResources().getString(R.string.posting));
            progressDialog.show();

            if (imageUri != null) {
                final StorageReference filerefrence = storageReference.child(System.currentTimeMillis()
                        + "." + getFileExtension(imageUri));
                // scaling the image
                int scaleDivider = 1;
                try {
                    Bitmap fullBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), imageUri);
                    int scaleWidth = fullBitmap.getWidth() / scaleDivider;
                    int scaleHeight = fullBitmap.getHeight() / scaleDivider;
                    byte[] downsizedImageBytes =
                            getDownsizedImageBytes(fullBitmap, scaleWidth, scaleHeight);

                    uploadTask = filerefrence.putBytes(downsizedImageBytes);
                } catch (IOException e) {
                    e.printStackTrace();
                }

static public byte[] getDownsizedImageBytes(Bitmap fullBitmap, int scaleWidth, int scaleHeight) throws IOException {

        Bitmap scaledBitmap = Bitmap.createScaledBitmap(fullBitmap, scaleWidth, scaleHeight, true);

        // 2. Instantiate the downsized image content as a byte[]
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);

        return baos.toByteArray();
    }

那么，对吗？

try {
                    Bitmap fullBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), imageUri);
                    ByteArrayOutputStream out = new ByteArrayOutputStream();
                    fullBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out); // Here 100 is the quality in percent of the image
                    Bitmap decoded = BitmapFactory.decodeStream(new ByteArrayInputStream(out.toByteArray()));

                    int scaleWidth = fullBitmap.getWidth() / scaleDivider;
                    int scaleHeight = fullBitmap.getHeight() / scaleDivider;
                    byte[] downsizedImageBytes =
                            getDownsizedImageBytes(fullBitmap, scaleWidth, scaleHeight);

                    uploadTask = filerefrence.putBytes(downsizedImageBytes);
                } catch (IOException e) {
                    e.printStackTrace();
                }

Answer 1

您可以像这样使用BitmapFactory 类来做到这一点

Bitmap original = MediaStore.Images.Media.getBitmap(this.getContentResolver(), imageUri)
ByteArrayOutputStream out = new ByteArrayOutputStream();
original.compress(Bitmap.CompressFormat.JPEG, 100, out); // Here 100 is the quality in percent of the image
Bitmap decoded = BitmapFactory.decodeStream(new ByteArrayInputStream(out.toByteArray()));

请注意，PNG 已经是一种无损格式，因此在压缩时不会有任何区别，如果您真的想看到使用 JPEG 的效果

质量接受 0 - 100

0 = 最大压缩（适用于小图像的最低质量）

100 = 最小压缩（适用于大图像的 MAX 质量）

感谢this 回答