/*
* 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.Matrix;
import android.view.View;
import androidx.annotation.NonNull;
final class CustomTransform {
private CustomTransform() {
}
/**
* Converts a {@link Matrix}, which represents a user provided custom preview transformation,
* to a {@link Transformation}.
*/
static Transformation getTransformation(@NonNull final View view,
@NonNull final Matrix matrix) {
final float[] values = new float[9];
matrix.getValues(values);
final float scaleX = values[Matrix.MSCALE_X];
final float scaleY = values[Matrix.MSCALE_Y];
final float originX = view.getX() + values[Matrix.MTRANS_X];
final float originY = view.getY() + values[Matrix.MTRANS_Y];
final float rotation = getRotationDegrees(values);
return new Transformation(scaleX, scaleY, originX, originY, rotation);
}
private static float getRotationDegrees(final float[] values) {
/*
A translation matrix can be represented as:
(1 0 transX)
(0 1 transX)
(0 0 1)
A rotation Matrix of ψ degrees can be represented as:
(cosψ -sinψ 0)
(sinψ cosψ 0)
(0 0 1)
A scale matrix can be represented as:
(scaleX 0 0)
(0 scaleY 0)
(0 0 0)
Meaning a transformed matrix can be represented as:
(scaleX * cosψ -scaleX * sinψ transX)
(scaleY * sinψ scaleY * cosψ transY)
(0 0 1)
Using the following 2 equalities:
scaleX * cosψ = matrix[0][0]
-scaleX * sinψ = matrix[0][1]
The following is deduced:
-tanψ = matrix[0][1] / matrix[0][0]
Or:
ψ = -arctan(matrix[0][1] / matrix[0][0])
*/
final double angle = -Math.atan2(values[Matrix.MSKEW_X], values[Matrix.MSCALE_X]);
return (float) Math.toDegrees(angle);
}
}