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Android 仿PhotoShop调色板应用(二) 透明度绘制之AlphaPatternDrawable
这里讲一下如何实现PS调色板中的透明度选择条.首先说一下要点:
1. 透明度选择条实际上是基于白色(0xffffffff)和灰色(0xffcbcbcb)之间的颜色区间选取, 由此我们可以实现一个半透明颜色的选取
2.该应用不仅可以做透明度颜色选取，也可以在应用中实现半透明的图像效果
下面看一下代码，主要是基于Drawable的重写：
/** Copyright (C) 2010 Daniel Nilsson** 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 net.margaritov.preference.colorpicker;import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;/*** This drawable that draws a simple white and gray chessboard pattern.* It's pattern you will often see as a background behind a* partly transparent image in many applications.* @author Daniel Nilsson*/
public class AlphaPatternDrawable extends Drawable {private int mRectangleSize = 10;private Paint mPaint = new Paint();private Paint mPaintWhite = new Paint();private Paint mPaintGray = new Paint();private int numRectanglesHorizontal;private int numRectanglesVertical;/*** Bitmap in which the pattern will be cahched.*/private Bitmap mBitmap;public AlphaPatternDrawable(int rectangleSize) {mRectangleSize = rectangleSize;mPaintWhite.setColor(0xffffffff);mPaintGray.setColor(0xffcbcbcb);}@Overridepublic void draw(Canvas canvas) {canvas.drawBitmap(mBitmap, null, getBounds(), mPaint);}@Overridepublic int getOpacity() {return 0;}@Overridepublic void setAlpha(int alpha) {throw new UnsupportedOperationException("Alpha is not supported by this drawwable.");}@Overridepublic void setColorFilter(ColorFilter cf) {throw new UnsupportedOperationException("ColorFilter is not supported by this drawwable.");}@Overrideprotected void onBoundsChange(Rect bounds) {super.onBoundsChange(bounds);int height = bounds.height();int width = bounds.width();numRectanglesHorizontal = (int) Math.ceil((width / mRectangleSize));numRectanglesVertical = (int) Math.ceil(height / mRectangleSize);generatePatternBitmap();}/*** This will generate a bitmap with the pattern* as big as the rectangle we were allow to draw on.* We do this to chache the bitmap so we don't need to* recreate it each time draw() is called since it* takes a few milliseconds.*/private void generatePatternBitmap(){if(getBounds().width() <= 0 || getBounds().height() <= 0){return;}mBitmap = Bitmap.createBitmap(getBounds().width(), getBounds().height(), Config.ARGB_8888);Canvas canvas = new Canvas(mBitmap);Rect r = new Rect();boolean verticalStartWhite = true;for (int i = 0; i <= numRectanglesVertical; i++) {boolean isWhite = verticalStartWhite;for (int j = 0; j <= numRectanglesHorizontal; j++) {r.top = i * mRectangleSize;r.left = j * mRectangleSize;r.bottom = r.top + mRectangleSize;r.right = r.left + mRectangleSize;canvas.drawRect(r, isWhite ? mPaintWhite : mPaintGray);isWhite = !isWhite;}verticalStartWhite = !verticalStartWhite;}}}这篇关于Android 仿PhotoShop调色板应用(二) 透明度绘制之AlphaPatternDrawable的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！
