java - 如何以编程方式更改图像的不透明度并将其保存在图库中

Question

我有两个图像彼此重叠，通过在运行时更改顶部图像的不透明度，然后组合这两个图像(意味着使这两个图像成为一个图像)并将其保存在图库中。在android studio中如何实现这一点？

Answer 1

如果图像是全屏的，只需制作您自己的屏幕截图即可。如果您愿意，有很多很棒的库可以为您执行此操作，或者您可以使用我放入名为 ImageHelper 的类中的简单代码，如下所示:

public static Bitmap takeScreenshotOfView(Activity context, Bitmap.CompressFormat compressFormat){
        Bitmap screenshot = null;

    try {
    // create bitmap screen capture
    View v1 = context.getWindow().getDecorView().getRootView();
    v1.setDrawingCacheEnabled(true);
    screenshot = Bitmap.createBitmap(v1.getDrawingCache());
    v1.setDrawingCacheEnabled(false);

    File imageFile = new File(context.getFilesDir() + File.separator + "A35_temp" + File.separator + "screenshot_temp");

    FileOutputStream outputStream = new FileOutputStream(imageFile);
    int quality = 100;

    screenshot.compress(compressFormat, quality, outputStream);
    outputStream.flush();
    outputStream.close();

} catch (Throwable e) {
    // Several error may come out with file handling or OOM
    e.printStackTrace();
}

    return screenshot;
}

然后像这样使用它:

Bitmap screenshot = ImageHelper.takeScreenshotOfView(this, Bitmap.CompressFormat.JPEG);

现在，如果您只需要捕获 ImageView 区域，您可以通过 View 获取它，也可以获取两个 ImageView 的父级，以便将它们包含在内。您还可以指定全屏，但从 imageView 起点和终点开始。这是我为管理各个区域的屏幕截图而编写的一些示例代码。

 private void convertCardToBitmap(boolean sendOnComplete){
    if(!mIsForStore) {
        Toast.makeText(this, getString(R.string.downloading_to_gallery), Toast.LENGTH_LONG).show();

    }

    CardView cardView = (CardView)findViewById(R.id.my_image_view_id);

    cardView.setDrawingCacheEnabled(true);

    cardView.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED), View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
    //cardView.measure((int)height, (int)width);
    cardView.layout(0, 0, cardView.getMeasuredWidth(), cardView.getMeasuredHeight());
    //cardView.layout(0, 0, (int)width, (int)height);
    cardView.buildDrawingCache(true);

    Bitmap bitmap = Bitmap.createBitmap(cardView.getDrawingCache());

    saveBitmapToGallery(bitmap, sendOnComplete);

}
private void saveBitmapToGallery(Bitmap cardToSave, boolean sendFileWhenSaved){
    OutputStream output;
    // Find the SD Card path
    File filepath = Environment.getExternalStorageDirectory();

    // Create a new folder in SD Card
    File dir = new File(filepath.getAbsolutePath() + "/MyAppPathDir/");
    dir.mkdirs();

    String imageName = mSelectedPerson.getFirstName() + "_" + mSelectedPerson.getLastName() + "_" + FileNameHelper.getNowTimeStamp();

    // Create a name for the saved image
    File file = new File(dir, imageName + ".jpg");

    try {
        int count = 1;
        //if file exists add 1 on the end and loop until finding a name that doesn't exist.
        while(file.exists()){
            file = new File(dir, imageName + count + ".jpg");
            count++;

        }

        output = new FileOutputStream(file);

        // Compress into png format image from 0% - 100%
        cardToSave.compress(Bitmap.CompressFormat.JPEG, 100, output);
        output.flush();
        output.close();

        addImageToGallery(file.getAbsolutePath());

        if(sendFileWhenSaved){
            Intent intent = getIntent();
            intent.putExtra(Globals.INTENT_KEYS.KEY_FILE_TO_SHARE, file.getAbsolutePath());
            intent.putExtra(Globals.INTENT_KEYS.KEY_SELECTED_IMAGE, mSelectedCardModel);
            setResult(RESULT_OK, intent);
            finish();

        } else if (mIsForStore) {
            uploadImageToS3(file.getAbsolutePath());

        } else{
            Toast.makeText(this, getString(R.string.saved_to_gallery), Toast.LENGTH_LONG).show();
            finish();

        }

    } catch (Exception e) {
        Toast.makeText(this, getString(R.string.error_failed_save_to_gallery) + e.getMessage(), Toast.LENGTH_LONG).show();

    }
}
private void uploadImageToS3(String filePath){
    final File newImageFile = new File(filePath);
    showProgressDialog(TAG, getString(R.string.loading_please_wait));

    //For auth route
    BasicAWSCredentials credentials = new BasicAWSCredentials(CognitoManager.getS3ClientID(), CognitoManager.getS3ClientSecret());

    AmazonS3Client s3 = new AmazonS3Client(credentials);
    TransferUtility transferUtility = new TransferUtility(s3, this);
    TransferObserver observer = transferUtility.upload(CognitoManager.getS3BucketName(), newImageFile.getName(), newImageFile);
    observer.setTransferListener(new TransferListener() {
        @Override
        public void onStateChanged(int id, TransferState state) {
            if(state.compareTo(TransferState.COMPLETED) == 0){
                String imgURLOfUploadComplete = "https://s3.amazonaws.com/" + CognitoManager.getS3BucketName() + "/" + newImageFile.getName();
                hideProgressDialog(TAG);
                Intent intent = new Intent();
                intent.putExtra(Globals.INTENT_KEYS.KEY_IMAGE_URL, imgURLOfUploadComplete);
                setResult(Activity.RESULT_OK, intent);
                if(newImageFile.exists()){
                    newImageFile.delete();

                }
                finish();

            }

        }
        @Override
        public void onProgressChanged(int id, long bytesCurrent, long bytesTotal) {
            if(bytesTotal != 0) {
                //For viewing progress
                int percentage = (int) (bytesCurrent / bytesTotal * 100);
            }
        }
        @Override
        public void onError(int id, Exception ex) {
            A35Log.e(TAG, getString(R.string.error_uploading_s3_part1) + id + getString(R.string.error_uploading_s3_part2) + ex.getMessage());
            hideProgressDialog(TAG);
            showDialogMessage(getString(error), getString(R.string.error_failed_create_image_alert_id) + error);

        }

    });

}
public void addImageToGallery(final String filePath) {
    ContentValues values = new ContentValues();

    values.put(MediaStore.Images.Media.DATE_TAKEN, System.currentTimeMillis());
    values.put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg");
    values.put(MediaStore.MediaColumns.DATA, filePath);

    getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);
}

希望有帮助:)。我会警告您，但当您启动 setDrawCacheEnabled 时，它可能会在屏幕上出现奇怪的行为，并导致您需要重绘，因为它有时似乎会消除约束。因此，我通常只是打开一个新的空白屏幕，其中包含要转换为图像的内容，完成工作然后关闭。

因此，只需看看它对您有何作用，然后决定从哪里开始。我尝试过的大多数库也有同样的问题，这就是为什么我只编写自己的库。