这个答案来自@Husayn 的答案。我已经添加了相关的示例代码部分。
用于预览和分析的相机图像尺寸因各种原因而异（例如特定于设备的显示尺寸/硬件/相机或特定于应用的视图和处理）
但是，有一些选项可以将处理图像大小和生成的 xy 坐标映射到预览大小和预览 xy 坐标。
为布局中的预览和分析叠加设置 DimensionRatio 3:4 布局，
例子：
<androidx.camera.view.PreviewView
android:id="@+id/view_finder"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintDimensionRatio="3:4"
app:layout_constraintTop_toTopOf="parent"/>
<com.loa.sepanex.scanner.view.GraphicOverlay
android:id="@+id/graphic_overlay"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintDimensionRatio="3:4"
app:layout_constraintTop_toTopOf="parent"/>
使用 AspectRatio.RATIO_4_3 设置预览和分析用例
例子：
viewFinder = view.findViewById(R.id.view_finder)
graphicOverlay = view.findViewById(R.id.graphic_overlay)
//...
preview = Preview.Builder()
.setTargetAspectRatio(AspectRatio.RATIO_4_3)
.setTargetRotation(rotation)
.build()
imageAnalyzer = ImageAnalysis.Builder()
.setTargetAspectRatio(AspectRatio.RATIO_4_3)
.setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
.setTargetRotation(rotation)
.build()
.also {
it.setAnalyzer(cameraExecutor, ImageAnalysis.Analyzer {
image ->
//val rotationDegrees = image.imageInfo.rotationDegrees
try {
val mediaImage: Image? = image.image
if (mediaImage != null) {
val imageForFaceDetectionProcess = InputImage.fromMediaImage(mediaImage, image.getImageInfo().getRotationDegrees())
//...
}
}
}
}
定义 scale 和 traslate API，用于获取分析图像 xy 坐标到预览 xy 坐标的映射，如下所示
val preview = viewFinder.getChildAt(0)
var previewWidth = preview.width * preview.scaleX
var previewHeight = preview.height * preview.scaleY
val rotation = preview.display.rotation
if (rotation == Surface.ROTATION_90 || rotation == Surface.ROTATION_270) {
val temp = previewWidth
previewWidth = previewHeight
previewHeight = temp
}
val isImageFlipped = lensFacing == CameraSelector.LENS_FACING_FRONT
val rotationDegrees: Int = imageProxy.getImageInfo().getRotationDegrees()
if (rotationDegrees == 0 || rotationDegrees == 180) {
graphicOverlay!!.setImageSourceInfo(
imageProxy.getWidth(), imageProxy.getHeight(), isImageFlipped)
} else {
graphicOverlay!!.setImageSourceInfo(
imageProxy.getHeight(), imageProxy.getWidth(), isImageFlipped)
}
:::
:::
float viewAspectRatio = (float) previewWidth / previewHeight;
float imageAspectRatio = (float) imageWidth / imageHeight;
postScaleWidthOffset = 0;
postScaleHeightOffset = 0;
if (viewAspectRatio > imageAspectRatio) {
// The image needs to be vertically cropped to be displayed in this view.
scaleFactor = (float) previewWidth / imageWidth;
postScaleHeightOffset = ((float) previewWidth / imageAspectRatio - previewHeight) / 2;
} else {
// The image needs to be horizontally cropped to be displayed in this view.
scaleFactor = (float) previewHeight / imageHeight;
postScaleWidthOffset = ((float) previewHeight * imageAspectRatio - previewWidth) / 2;
}
transformationMatrix.reset();
transformationMatrix.setScale(scaleFactor, scaleFactor);
transformationMatrix.postTranslate(-postScaleWidthOffset, -postScaleHeightOffset);
if (isImageFlipped) {
transformationMatrix.postScale(-1f, 1f, previewWidth / 2f, previewHeight / 2f);
}
:::
:::
public float scale(float imagePixel) {
return imagePixel * overlay.scaleFactor;
}
public float translateX(float x) {
if (overlay.isImageFlipped) {
return overlay.getWidth() - (scale(x) - overlay.postScaleWidthOffset);
} else {
return scale(x) - overlay.postScaleWidthOffset;
}
}
public float translateY(float y) {
return scale(y) - overlay.postScaleHeightOffset;
}
使用 translateX 和 translateY 方法将基于分析图像的数据绘制到预览中
例子：
for (FaceContour contour : face.getAllContours()) {
for (PointF point : contour.getPoints()) {
canvas.drawCircle(translateX(point.x), translateY(point.y), FACE_POSITION_RADIUS, facePositionPaint);
}
}