PreviewCorrector.java
/*
* Copyright 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.camera.view.preview.transform;
import android.graphics.Point;
import android.util.Pair;
import android.util.Size;
import android.view.Display;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.camera.view.preview.transform.transformation.PreviewCorrectionTransformation;
/** Corrects a camera preview by scaling and/or rotating it so that it matches the display. */
final class PreviewCorrector {
private PreviewCorrector() {
}
/**
* Corrects a camera preview by scaling and rotating it.
*
* @param container Preview container
* @param preview Preview view (a {@link android.view.TextureView} or
* {@link android.view.SurfaceView})
* @param bufferSize Camera output size
*/
@NonNull
static PreviewCorrectionTransformation getCorrectionTransformation(
@NonNull final View container, @NonNull final View preview,
@NonNull final Size bufferSize) {
final int rotation = (int) RotationTransform.getRotationDegrees(preview);
final Pair<Float, Float> scaleXY = getCorrectionScale(container, preview,
bufferSize);
return new PreviewCorrectionTransformation(scaleXY.first, scaleXY.second, -rotation);
}
/**
* Computes the scales on both the x and y axes so that the preview can be corrected.
*
* @param container Preview container
* @param preview Preview view (a {@link android.view.TextureView} or
* {@link android.view.SurfaceView})
* @param bufferSize Camera output size
* @return The scales on both the x and y axes so that the preview can be corrected.
*/
private static Pair<Float, Float> getCorrectionScale(@NonNull final View container,
@NonNull final View preview, @NonNull final Size bufferSize) {
// Scaling only makes sense when none of the dimensions are equal to zero. In the
// opposite case, a default scale of 1 is returned,
if (container.getWidth() == 0 || container.getHeight() == 0 || preview.getWidth() == 0
|| preview.getHeight() == 0 || bufferSize.getWidth() == 0
|| bufferSize.getHeight() == 0) {
return new Pair<>(1F, 1F);
}
final int bufferWidth;
final int bufferHeight;
if (isNaturalPortrait(preview)) {
bufferWidth = bufferSize.getHeight();
bufferHeight = bufferSize.getWidth();
} else {
bufferWidth = bufferSize.getWidth();
bufferHeight = bufferSize.getHeight();
}
// Scale the buffers back to the original output size.
float scaleX = bufferWidth / (float) preview.getWidth();
float scaleY = bufferHeight / (float) preview.getHeight();
return new Pair<>(scaleX, scaleY);
}
/**
* Determines whether the current device is a natural portrait-oriented device
*
* <p>
* Using the current app's window to determine whether the device is a natural
* portrait-oriented device doesn't work in all scenarios, one example of this is multi-window
* mode.
* Taking a natural portrait-oriented device in multi-window mode, rotating it 90 degrees (so
* that it's in landscape), with the app open, and its window's width being smaller than its
* height. Using the app's width and height would determine that the device isn't
* naturally portrait-oriented, where in fact it is, which is why it is important to use the
* size of the device instead.
* </p>
*
* @param view A {@link View} used to get the current {@link Display}.
* @return Whether the device is naturally portrait-oriented.
*/
private static boolean isNaturalPortrait(@NonNull final View view) {
final Display display = view.getDisplay();
if (display == null) {
return true;
}
final Point deviceSize = new Point();
display.getRealSize(deviceSize);
final int width = deviceSize.x;
final int height = deviceSize.y;
final int rotationDegrees = (int) RotationTransform.getRotationDegrees(view);
return ((rotationDegrees == 0 || rotationDegrees == 180) && width < height) || (
(rotationDegrees == 90 || rotationDegrees == 270) && width >= height);
}
}