wallpaper/util/WallpaperCropUtils.java

/*
 * Copyright (C) 2017 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 com.android.wallpaper.util;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Point;
import android.graphics.PointF;
import android.graphics.Rect;
import android.os.Build.VERSION;
import android.os.Build.VERSION_CODES;
import android.view.Display;
import android.view.View;

/**
 * Static utility methods for wallpaper cropping operations.
 */
public final class WallpaperCropUtils {

    private static final float WALLPAPER_SCREENS_SPAN = 2f;
    private static final float ASPECT_RATIO_LANDSCAPE = 16 / 10f;
    private static final float ASPECT_RATIO_PORTRAIT = 10 / 16f;
    private static final float WALLPAPER_WIDTH_TO_SCREEN_RATIO_LANDSCAPE = 1.2f;
    private static final float WALLPAPER_WIDTH_TO_SCREEN_RATIO_PORTRAIT = 1.5f;

    // Suppress default constructor for noninstantiability.
    private WallpaperCropUtils() {
        throw new AssertionError();
    }

    /**
     * Calculates parallax travel (i.e., extra width) for a screen with the given resolution.
     */
    public static float wallpaperTravelToScreenWidthRatio(int width, int height) {
        float aspectRatio = width / (float) height;

        // At an aspect ratio of 16/10, the wallpaper parallax effect should span 1.2 * screen width
        // At an aspect ratio of 10/16, the wallpaper parallax effect should span 1.5 * screen width
        // We will use these two data points to extrapolate how much the wallpaper parallax effect
        // to span (i.e., travel) at any aspect ratio. We use the following two linear formulas,
        // where
        // the coefficient on x is the aspect ratio (width/height):
        //   (16/10)x + y = 1.2
        //   (10/16)x + y = 1.5
        // We solve for x and y and end up with a final formula:
        float x = (WALLPAPER_WIDTH_TO_SCREEN_RATIO_LANDSCAPE
                - WALLPAPER_WIDTH_TO_SCREEN_RATIO_PORTRAIT)
                / (ASPECT_RATIO_LANDSCAPE - ASPECT_RATIO_PORTRAIT);
        float y = WALLPAPER_WIDTH_TO_SCREEN_RATIO_PORTRAIT - x * ASPECT_RATIO_PORTRAIT;
        return x * aspectRatio + y;
    }

    /**
     * Calculates ideal crop surface size for a device such that there is room for parallax in both
     * landscape and portrait screen orientations.
     */
    public static Point getDefaultCropSurfaceSize(Resources resources, Display display) {
        Point minDims = new Point();
        Point maxDims = new Point();
        display.getCurrentSizeRange(minDims, maxDims);

        int maxDim = Math.max(maxDims.x, maxDims.y);
        int minDim = Math.max(minDims.x, minDims.y);

        if (VERSION.SDK_INT >= VERSION_CODES.JELLY_BEAN_MR1) {
            Point realSize = new Point();
            display.getRealSize(realSize);
            maxDim = Math.max(realSize.x, realSize.y);
            minDim = Math.min(realSize.x, realSize.y);
        }

        final int defaultWidth, defaultHeight;
        if (resources.getConfiguration().smallestScreenWidthDp >= 720) {
            defaultWidth = (int) (maxDim * wallpaperTravelToScreenWidthRatio(maxDim, minDim));
            defaultHeight = maxDim;
        } else {
            defaultWidth = Math.max((int) (minDim * WALLPAPER_SCREENS_SPAN), maxDim);
            defaultHeight = maxDim;
        }

        return new Point(defaultWidth, defaultHeight);
    }

    /**
     * Calculates the relative position between an outer and inner rectangle when the outer one is
     * center-cropped to the inner one.
     *
     * @param outer      Size of outer rectangle as a Point (x,y).
     * @param inner      Size of inner rectangle as a Point (x,y).
     * @param alignStart Whether the inner rectangle should be aligned to the start of the layout
     *                   with the outer one and ignore horizontal centering.
     * @param isRtl      Whether the layout direction is RTL (or false for LTR).
     * @return Position relative to the top left corner of the outer rectangle, where the size of
     * each rectangle is represented by Points, in coordinates (x,y) relative to the outer rectangle
     * where the top left corner is (0,0)
     * @throws IllegalArgumentException if inner rectangle is not contained within outer rectangle
     *                                  which would return a position with at least one negative
     *                                  coordinate.
     */
    public static Point calculateCenterPosition(Point outer, Point inner, boolean alignStart,
            boolean isRtl) {
        if (inner.x > outer.x || inner.y > outer.y) {
            throw new IllegalArgumentException("Inner rectangle " + inner + " should be contained"
                    + " completely within the outer rectangle " + outer + ".");
        }

        Point relativePosition = new Point();

        if (alignStart) {
            relativePosition.x = isRtl ? outer.x - inner.x : 0;
        } else {
            relativePosition.x = Math.round((outer.x - inner.x) / 2f);
        }
        relativePosition.y = Math.round((outer.y - inner.y) / 2f);

        return relativePosition;
    }

    /**
     * Calculates the minimum zoom such that the maximum surface area of the outer rectangle is
     * visible within the inner rectangle.
     *
     * @param outer Size of outer rectangle as a Point (x,y).
     * @param inner Size of inner rectangle as a Point (x,y).
     */
    public static float calculateMinZoom(Point outer, Point inner) {
        float minZoom;
        if (inner.x / (float) inner.y > outer.x / (float) outer.y) {
            minZoom = inner.x / (float) outer.x;
        } else {
            minZoom = inner.y / (float) outer.y;
        }
        return minZoom;
    }

    /**
     * Calculates the center area of the outer rectangle which is visible in the inner rectangle
     * after applying the minimum zoom.
     *
     * @param outer the size of outer rectangle as a Point (x,y).
     * @param inner the size of inner rectangle as a Point (x,y).
     */
    public static Rect calculateVisibleRect(Point outer, Point inner) {
        PointF visibleRectCenter = new PointF(outer.x / 2f, outer.y / 2f);
        if (inner.x / (float) inner.y > outer.x / (float) outer.y) {
            float minZoom = inner.x / (float) outer.x;
            float visibleRectHeight = inner.y / minZoom;
            return new Rect(0, (int) (visibleRectCenter.y - visibleRectHeight / 2),
                    outer.x, (int) (visibleRectCenter.y + visibleRectHeight / 2));
        } else {
            float minZoom = inner.y / (float) outer.y;
            float visibleRectWidth = inner.x / minZoom;
            return new Rect((int) (visibleRectCenter.x - visibleRectWidth / 2),
                    0, (int) (visibleRectCenter.x + visibleRectWidth / 2), outer.y);
        }
    }

    /**
     * Calculates {@link Rect} of the wallpaper which we want to crop to in physical pixel terms
     * (i.e., scaled to current zoom).
     *
     * @param rawWallpaperSize        the size of the raw wallpaper as a Point (x,y).
     * @param visibleRawWallpaperRect the area of the raw wallpaper which is expected to see.
     * @param wallpaperZoom           the factor which is used to scale the raw wallpaper.
     */
    public static Rect calculateCropRect(Context context, Display display, Point rawWallpaperSize,
                                         Rect visibleRawWallpaperRect, float wallpaperZoom) {
        int scaledWallpaperWidth = (int) (rawWallpaperSize.x * wallpaperZoom);
        int scaledWallpaperHeight = (int) (rawWallpaperSize.y * wallpaperZoom);
        int scrollX = (int) (visibleRawWallpaperRect.left * wallpaperZoom);
        int scrollY = (int) (visibleRawWallpaperRect.top * wallpaperZoom);

        visibleRawWallpaperRect.set(0, 0, scaledWallpaperWidth, scaledWallpaperHeight);

        Point screenSize = ScreenSizeCalculator.getInstance().getScreenSize(display);
        // Crop rect should start off as the visible screen and then include extra width and height
        // if available within wallpaper at the current zoom.
        Rect cropRect = new Rect(scrollX, scrollY, scrollX + screenSize.x, scrollY + screenSize.y);

        Point defaultCropSurfaceSize = WallpaperCropUtils.getDefaultCropSurfaceSize(
                context.getResources(), display);
        int extraWidth = defaultCropSurfaceSize.x - screenSize.x;
        int extraHeightTopAndBottom = (int) ((defaultCropSurfaceSize.y - screenSize.y) / 2f);

        // Try to increase size of screenRect to include extra width depending on the layout
        // direction.
        if (isRtl(context)) {
            cropRect.left = Math.max(cropRect.left - extraWidth, visibleRawWallpaperRect.left);
        } else {
            cropRect.right = Math.min(cropRect.right + extraWidth, visibleRawWallpaperRect.right);
        }

        // Try to increase the size of the cropRect to to include extra height.
        int availableExtraHeightTop = cropRect.top - Math.max(
                visibleRawWallpaperRect.top,
                cropRect.top - extraHeightTopAndBottom);
        int availableExtraHeightBottom = Math.min(
                visibleRawWallpaperRect.bottom,
                cropRect.bottom + extraHeightTopAndBottom) - cropRect.bottom;

        int availableExtraHeightTopAndBottom =
                Math.min(availableExtraHeightTop, availableExtraHeightBottom);
        cropRect.top -= availableExtraHeightTopAndBottom;
        cropRect.bottom += availableExtraHeightTopAndBottom;

        return cropRect;
    }

    /**
     * Resize the wallpaper size so it's new size fits in a outWidth by outHeight rectangle.
     *
     * @param wallpaperSize Rectangle with the current wallpaper size. It will be resized.
     * @param outWidth      the width of the rectangle in which the wallpaperSize needs to fit.
     * @param outHeight     the height of the rectangle in which the wallpaperSize needs to fit.
     */
    public static void fitToSize(Rect wallpaperSize, int outWidth, int outHeight) {
        if (wallpaperSize.isEmpty()) {
            return;
        }
        float maxSizeOut = Math.max(outWidth, outHeight);
        float maxSizeIn = Math.max(wallpaperSize.width(), wallpaperSize.height());
        float scale = maxSizeOut / maxSizeIn;

        // Scale the wallpaper size
        if (scale != 1.0f) {
            wallpaperSize.left = (int) (wallpaperSize.left * scale + 0.5f);
            wallpaperSize.top = (int) (wallpaperSize.top * scale + 0.5f);
            wallpaperSize.right = (int) (wallpaperSize.right * scale + 0.5f);
            wallpaperSize.bottom = (int) (wallpaperSize.bottom * scale + 0.5f);
        }
    }

    /**
     * Returns whether layout direction is RTL (or false for LTR). Since native RTL layout support
     * was added in API 17, returns false for versions lower than 17.
     */
    private static boolean isRtl(Context context) {
        return context.getResources().getConfiguration().getLayoutDirection()
                == View.LAYOUT_DIRECTION_RTL;
    }
}