android - 在 Android 上模糊图像中的区域(在 Java 中)

Question

在我的 Android 应用程序中，我正在以编程方式从后台服务捕获屏幕截图。我以位图的形式获取它。

接下来，我使用以下 Android 框架 API 获取感兴趣区域 (ROI) 的坐标:

Rect ROI = new Rect();
viewNode.getBoundsInScreen(ROI);

在这里，getBoundsInScreen()在 Android 中相当于 Javascript 函数 getBoundingClientRect() .

一个Rect在Android中具有以下属性:

rect.top
rect.left
rect.right
rect.bottom
rect.height()
rect.width()
rect.centerX()    /* rounded off to integer */
rect.centerY()
rect.exactCenterX()    /* exact value in float */
rect.exactCenterY()

What does top, left, right and bottom mean in Android Rect object

而 Rect在OpenCV中具有以下属性

rect.width
rect.height
rect.x    /* x coordinate of the top-left corner  */
rect.y    /* y coordinate of the top-left corner  */

现在，在执行任何 OpenCV 相关操作之前，我们需要将 Android Rect 转换为 OpenCV Rect。

Understanding how actually drawRect or drawing coordinates work in Android

有两种方法可以将 Android 矩形 转换为 OpenCV 矩形(如 Karl Phillip 在他的回答中所建议的)。两者生成相同的值并产生相同的结果:

/* Compute the top-left corner using the center point of the rectangle. */
int x = androidRect.centerX() - (androidRect.width() / 2);
int y = androidRect.centerY() - (androidRect.height() / 2);

// OR simply use the already available member variables:
x = androidRect.left;
y = androidRect.top;

int w = androidRect.width();
int h = androidRect.height();

org.opencv.core.Rect roi = new org.opencv.core.Rect(x, y, w, h);

现在我正在执行的 OpenCV 操作之一是 blurring the ROI within the screenshot :

Mat originalMat = new Mat();
Bitmap configuredBitmap32 = originalBitmap.copy(Bitmap.Config.ARGB_8888, true);
Utils.bitmapToMat(configuredBitmap32, originalMat);
Mat ROIMat = originalMat.submat(roi).clone();
Imgproc.GaussianBlur(ROIMat, ROIMat, new org.opencv.core.Size(0, 0), 5, 5);
ROIMat.copyTo(originalMat.submat(roi));

Bitmap blurredBitmap = Bitmap.createBitmap(originalMat.cols(), originalMat.rows(), Bitmap.Config.ARGB_8888);
Utils.matToBitmap(originalMat, blurredBitmap);

This brings us very close to the desired result. Almost there, but not quite. The area just BENEATH the targeted region is blurred.

例如，如果目标感兴趣区域是密码字段，则上述代码会产生以下结果:

左侧为Microsoft Live 投资返回率，右侧为Pinterest 投资返回率:

可以看出，ROI下方的区域变得模糊。

So my question is, finally, why isn't the exact region of interest blurred?

• The co-ordinates obtained through the Android API getBoundsInScreen() appear to be correct.
• Converting an Android Rect to an OpenCV Rect also appears to be correct. Or is it?
• The code for blurring a region of interest also appears to be correct. Is there another way to do the same thing?

注意:我已经提供了实际的全尺寸屏幕截图。为了适应这篇文章，它们已经缩小了 50%，但除此之外，它们与我在 Android 设备上得到的一模一样。

Answer 1

如果我没记错的话，OpenCV的Rect假设x和y指定矩形的左上角:

/* Compute the top-left corner using the center point of the rectangle
 * TODO: take care of float to int conversion
 */
int x = androidRect.centerX() - (androidRect.width() / 2);
int y = androidRect.centerY() - (androidRect.height() / 2);

// OR simply use the already available member variables:
x = androidRect.left;
y = androidRect.top;

int w = androidRect.width();
int h = androidRect.height();

org.opencv.core.Rect roi = new org.opencv.core.Rect(x, y, w, h);