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Normalizing app icons based on the standard icon guidelines

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Bug: 18245189
Change-Id: Iaadcddbe3f966733a13b2e1fb60ba09a8b3aef9a
This commit is contained in:
Sunny Goyal
2015-09-17 14:59:10 -07:00
parent aa4011e63e
commit fc21830e6b
4 changed files with 261 additions and 8 deletions
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src/com/android/launcher3/util/IconNormalizer.java
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/*
* Copyright (C) 2015 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.launcher3.util;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import com.android.launcher3.LauncherAppState;
import java.nio.ByteBuffer;
public class IconNormalizer {
// Ratio of icon visible area to full icon size for a square shaped icon
private static final float MAX_SQUARE_AREA_FACTOR = 359.0f / 576;
// Ratio of icon visible area to full icon size for a circular shaped icon
private static final float MAX_CIRCLE_AREA_FACTOR = 380.0f / 576;
private static final float CIRCLE_AREA_BY_RECT = (float) Math.PI / 4;
// Slope used to calculate icon visible area to full icon size for any generic shaped icon.
private static final float LINEAR_SCALE_SLOPE =
(MAX_CIRCLE_AREA_FACTOR - MAX_SQUARE_AREA_FACTOR) / (1 - CIRCLE_AREA_BY_RECT);
private static final int MIN_VISIBLE_ALPHA = 40;
private static final Object LOCK = new Object();
private static IconNormalizer sIconNormalizer;
private final int mMaxSize;
private final Bitmap mBitmap;
private final Canvas mCanvas;
private final byte[] mPixels;
// for each y, stores the position of the leftmost x and the rightmost x
private final float[] mLeftBorder;
private final float[] mRightBorder;
private IconNormalizer() {
// Use twice the icon size as maximum size to avoid scaling down twice.
mMaxSize = LauncherAppState.getInstance().getInvariantDeviceProfile().iconBitmapSize * 2;
mBitmap = Bitmap.createBitmap(mMaxSize, mMaxSize, Bitmap.Config.ALPHA_8);
mCanvas = new Canvas(mBitmap);
mPixels = new byte[mMaxSize * mMaxSize];
mLeftBorder = new float[mMaxSize];
mRightBorder = new float[mMaxSize];
}
/**
* Returns the amount by which the {@param d} should be scaled (in both dimensions) so that it
* matches the design guidelines for a launcher icon.
*
* We first calculate the convex hull of the visible portion of the icon.
* This hull then compared with the bounding rectangle of the hull to find how closely it
* resembles a circle and a square, by comparing the ratio of the areas. Note that this is not an
* ideal solution but it gives satisfactory result without affecting the performance.
*
* This closeness is used to determine the ratio of hull area to the full icon size.
* Refer {@link #MAX_CIRCLE_AREA_FACTOR} and {@link #MAX_SQUARE_AREA_FACTOR}
*/
public synchronized float getScale(Drawable d) {
int width = d.getIntrinsicWidth();
int height = d.getIntrinsicHeight();
if (width <= 0 || height <= 0) {
width = width <= 0 || width > mMaxSize ? mMaxSize : width;
height = height <= 0 || height > mMaxSize ? mMaxSize : height;
} else if (width > mMaxSize || height > mMaxSize) {
int max = Math.max(width, height);
width = mMaxSize * width / max;
height = mMaxSize * height / max;
}
mBitmap.eraseColor(Color.TRANSPARENT);
d.setBounds(0, 0, width, height);
d.draw(mCanvas);
ByteBuffer buffer = ByteBuffer.wrap(mPixels);
buffer.rewind();
mBitmap.copyPixelsToBuffer(buffer);
// Overall bounds of the visible icon.
int topY = -1;
int bottomY = -1;
int leftX = mMaxSize + 1;
int rightX = -1;
// Create border by going through all pixels one row at a time and for each row find
// the first and the last non-transparent pixel. Set those values to mLeftBorder and
// mRightBorder and use -1 if there are no visible pixel in the row.
// buffer position
int index = 0;
// buffer shift after every row, width of buffer = mMaxSize
int rowSizeDiff = mMaxSize - width;
// first and last position for any row.
int firstX, lastX;
for (int y = 0; y < height; y++) {
firstX = lastX = -1;
for (int x = 0; x < width; x++) {
if ((mPixels[index] & 0xFF) > MIN_VISIBLE_ALPHA) {
if (firstX == -1) {
firstX = x;
}
lastX = x;
}
index++;
}
index += rowSizeDiff;
mLeftBorder[y] = firstX;
mRightBorder[y] = lastX;
// If there is at least one visible pixel, update the overall bounds.
if (firstX != -1) {
bottomY = y;
if (topY == -1) {
topY = y;
}
leftX = Math.min(leftX, firstX);
rightX = Math.max(rightX, lastX);
}
}
if (topY == -1 || rightX == -1) {
// No valid pixels found. Do not scale.
return 1;
}
convertToConvexArray(mLeftBorder, 1, topY, bottomY);
convertToConvexArray(mRightBorder, -1, topY, bottomY);
// Area of the convex hull
float area = 0;
for (int y = 0; y < height; y++) {
if (mLeftBorder[y] <= -1) {
continue;
}
area += mRightBorder[y] - mLeftBorder[y] + 1;
}
// Area of the rectangle required to fit the convex hull
float rectArea = (bottomY + 1 - topY) * (rightX + 1 - leftX);
float hullByRect = area / rectArea;
float scaleRequired;
if (hullByRect < CIRCLE_AREA_BY_RECT) {
scaleRequired = MAX_CIRCLE_AREA_FACTOR;
} else {
scaleRequired = MAX_SQUARE_AREA_FACTOR + LINEAR_SCALE_SLOPE * (1 - hullByRect);
}
float areaScale = area / (width * height);
// Use sqrt of the final ratio as the images is scaled across both width and height.
float scale = areaScale > scaleRequired ? (float) Math.sqrt(scaleRequired / areaScale) : 1;
return scale;
}
/**
* Modifies {@param xCordinates} to represent a convex border. Fills in all missing values
* (except on either ends) with appropriate values.
* @param xCordinates map of x coordinate per y.
* @param direction 1 for left border and -1 for right border.
* @param topY the first Y position (inclusive) with a valid value.
* @param bottomY the last Y position (inclusive) with a valid value.
*/
private static void convertToConvexArray(
float[] xCordinates, int direction, int topY, int bottomY) {
int total = xCordinates.length;
// The tangent at each pixel.
float[] angles = new float[total - 1];
int first = topY; // First valid y coordinate
int last = -1; // Last valid y coordinate which didn't have a missing value
float lastAngle = Float.MAX_VALUE;
for (int i = topY + 1; i <= bottomY; i++) {
if (xCordinates[i] <= -1) {
continue;
}
int start;
if (lastAngle == Float.MAX_VALUE) {
start = first;
} else {
float currentAngle = (xCordinates[i] - xCordinates[last]) / (i - last);
start = last;
// If this position creates a concave angle, keep moving up until we find a
// position which creates a convex angle.
if ((currentAngle - lastAngle) * direction < 0) {
while (start > first) {
start --;
currentAngle = (xCordinates[i] - xCordinates[start]) / (i - start);
if ((currentAngle - angles[start]) * direction >= 0) {
break;
}
}
}
}
// Reset from last check
lastAngle = (xCordinates[i] - xCordinates[start]) / (i - start);
// Update all the points from start.
for (int j = start; j < i; j++) {
angles[j] = lastAngle;
xCordinates[j] = xCordinates[start] + lastAngle * (j - start);
}
last = i;
}
}
public static IconNormalizer getInstance() {
synchronized (LOCK) {
if (sIconNormalizer == null) {
sIconNormalizer = new IconNormalizer();
}
}
return sIconNormalizer;
}
}