颜色梯度曼德尔布罗Android应用程序无法正常工作 [英] Color gradient for Mandelbrot Android application doesn't work

问题描述

我试图编程Mandelbrot集为Android。
我试图把它画在画布上。它的工作原理，但我希望有一个颜色渐变。
这是我的code：

 包de.turbofractal;进口android.app.AlertDialog;
进口android.content.Context;
进口android.content.DialogInterface;
进口android.graphics.Canvas;
进口android.graphics.Color;
进口android.graphics.Paint;
进口android.view.View;
公共类FractalView扩展视图{
   私人诠释N，G，XMAX，YMAX;
   私人浮动ZR，ZRH，ZR0，紫，zi0，AR，BR，AI，双向;
   私人INT [] [] = Iterationen新INT [2560] [1440]
   私人涂料粉刷;   公共FractalView（上下文的背景下）{
      超级（上下文）;
      油漆=新的油漆（）;
      AR = -2; BR = 2; AI = -2; BI = 2;
   }   @覆盖
   保护无效的onDraw（帆布油画）{
       G = 20;
       为（中间体XX = 1; XX＆下; = XMAX; XX ++）{
           对于（INT YY = 1; YY＆LT; = YMAX; YY ++）{
               schirmzupap（AR，BR，BI，AI，XX，YY，XMAX，YMAX）;
               N = 1;
               ZR0 = ZR;
               zi0 =子;
               而（（N＆LT; G）和放大器;及（ZR * ZR +紫紫* 4;））{
                   ZRH = ZR;
                   ZR =（ZR * ZR）-zi *字+ ZR0;
                   紫= ZRH *子+子* ZRH + zi0;
                   Ñ​​++;
               }
               paint.setARGB（255,0,0，Math.round（（N / G）* 255））; //＆LT; --------------------这是那里的颜色渐变应创建。但仅PROGRAMM画满蓝（0,0,255）。这是为什么？
               canvas.drawPoint（XX，YY，油漆）;
           }        }
        无效（）;
   }
   私人无效schirmzupap（浮点AX，BX浮球，浮球AY，由浮球，诠释xschirm，诠释yschirm，诠释W，INT高）{
       ZR = xschirm *（BX-AX）/ W + AX​​;
       紫= yschirm *（AY-BY）由/ H +;
   }   @覆盖
   公共无效onSizeChanged（INT W，INT小时，INT oldW，诠释oldH）{
      XMAX = W-1;
      YMAX = -1;
   }
}
 

编辑：
这是它是如何由Eclipse仿真得出：
http://i53.tinypic.com/2mwfs7c.png

但我想它要绘制这样（用Delphi编程）：
http://i53.tinypic.com/ehg2et.png

解决方案

  paint.setARGB（255,0,0，Math.round（（N / G）* 255））;
 

为 setARGB 是 A lpha，研究版，先按g 颖和 b 攻略 - 你只给阿尔法和蓝色的参数提供值。

在 B 参数，既 N 和先按g 是整型参数，所以，当你把他们，你会得到一个整数结果，的不的双。 （请参见<一个href=\"http://stackoverflow.com/questions/3144610/java-integer-division-how-do-you-produce-a-double\">Java整数除法，你如何制作一张双人床？），这意味着你只能得到的结果，这是不是你想要的整数部分。铸造 N 或先按g 来一张双人床和它应该工作。

I'm trying to to program the Mandelbrot set for Android. I try to draw it on a Canvas. It works, but I want to have a color gradient. This is my code:

package de.turbofractal;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;


public class FractalView extends View {
   private int n,g,xMax,yMax;
   private float zr,zrh,zr0,zi,zi0,ar,br,ai,bi;
   private int[][] Iterationen = new int[2560][1440];
   private Paint paint;

   public FractalView(Context context) {
      super(context);
      paint = new Paint();
      ar=-2; br=2; ai=-2; bi=2;
   }

   @Override
   protected void onDraw(Canvas canvas) {
       g = 20;
       for(int xx = 1; xx <= xMax; xx++) {
           for(int yy = 1; yy <= yMax; yy++) {
               schirmzupap(ar,br,bi,ai,xx,yy,xMax,yMax);
               n = 1;
               zr0 = zr;
               zi0 = zi;
               while ((n<g) && (zr*zr+zi*zi<4)) {
                   zrh = zr;
                   zr = (zr*zr)-zi*zi+zr0;
                   zi = zrh*zi+zi*zrh+zi0;
                   n++;
               }
               paint.setARGB(255,0,0,Math.round((n/g)*255));  //<--------------------this is where the color gradient should be created. But the programm only draws full blue (0,0,255). Why is that?
               canvas.drawPoint(xx, yy, paint);            
           }

        }
        invalidate();
   }      


   private void schirmzupap(float ax,float bx,float ay,float by,int xschirm,int yschirm,int w,int h) {
       zr = xschirm*(bx-ax)/w+ax;
       zi = yschirm*(ay-by)/h+by;
   } 

   @Override
   public void onSizeChanged(int w, int h, int oldW, int oldH) {
      xMax = w-1;
      yMax = h-1;
   }
}

Edit: This is how it is drawn by the eclipse emulator: http://i53.tinypic.com/2mwfs7c.png

But I want it to be drawn like this (programmed with Delphi): http://i53.tinypic.com/ehg2et.png

解决方案

paint.setARGB(255,0,0,Math.round((n/g)*255));  

The arguments for setARGB are alpha, red, green, and blue - you are only supplying values to the alpha and blue parameters.

Inside the b parameter, both n and g are integer parameters, so when you divide them, you will get an integer result, not a double. (See "Java Integer Division, How do you produce a double?") This means you only get the whole number part of the result, which isn't what you want. Cast n or g to a double and it should work.

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