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      1 /*
      2  * Copyright 2012 AndroidPlot.com
      3  *
      4  *    Licensed under the Apache License, Version 2.0 (the "License");
      5  *    you may not use this file except in compliance with the License.
      6  *    You may obtain a copy of the License at
      7  *
      8  *        http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  *    Unless required by applicable law or agreed to in writing, software
     11  *    distributed under the License is distributed on an "AS IS" BASIS,
     12  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  *    See the License for the specific language governing permissions and
     14  *    limitations under the License.
     15  */
     16 
     17 package com.androidplot.util;
     18 
     19 import android.graphics.PointF;
     20 import android.graphics.RectF;
     21 
     22 /**
     23  * Utility methods for converting pixel coordinates into real values and vice versa.
     24  */
     25 public class ValPixConverter {
     26     private static final int ZERO = 0;
     27 
     28 
     29     public static float valToPix(double val, double min, double max, float lengthPix, boolean flip) {
     30         if(lengthPix <= ZERO) {
     31             throw new IllegalArgumentException("Length in pixels must be greater than 0.");
     32         }
     33         double range = range(min, max);
     34         double scale = lengthPix / range;
     35         double raw = val - min;
     36         float pix = (float)(raw * scale);
     37 
     38         if(flip) {
     39             pix = (lengthPix - pix);
     40         }
     41         return pix;
     42     }
     43 
     44     public static double range(double min, double max) {
     45         return (max-min);
     46     }
     47 
     48 
     49     public static double valPerPix(double min, double max, float lengthPix) {
     50         double valRange = range(min, max);
     51         return valRange/lengthPix;
     52     }
     53 
     54     /**
     55      * Convert a value in pixels to the type passed into min/max
     56      * @param pix
     57      * @param min
     58      * @param max
     59      * @param lengthPix
     60      * @param flip True if the axis should be reversed before calculated. This is the case
     61      * with the y axis for screen coords.
     62      * @return
     63      */
     64     public static double pixToVal(float pix, double min, double max, float lengthPix, boolean flip) {
     65         if(pix < ZERO) {
     66             throw new IllegalArgumentException("pixel values cannot be negative.");
     67         }
     68 
     69         if(lengthPix <= ZERO) {
     70             throw new IllegalArgumentException("Length in pixels must be greater than 0.");
     71         }
     72         float pMult = pix;
     73         if(flip) {
     74             pMult = lengthPix - pix;
     75         }
     76         double range = range(min, max);
     77         return ((range / lengthPix) * pMult) + min;
     78     }
     79 
     80     /**
     81      * Converts a real value into a pixel value.
     82      * @param x Real d (domain) component of the point to convert.
     83      * @param y Real y (range) component of the point to convert.
     84      * @param plotArea
     85      * @param minX Minimum visible real value on the d (domain) axis.
     86      * @param maxX Maximum visible real value on the y (domain) axis.
     87      * @param minY Minimum visible real value on the y (range) axis.
     88      * @param maxY Maximum visible real value on the y (range axis.
     89      * @return
     90      */
     91     public static PointF valToPix(Number x, Number y, RectF plotArea, Number minX, Number maxX, Number minY, Number maxY) {
     92         float pixX = ValPixConverter.valToPix(x.doubleValue(), minX.doubleValue(), maxX.doubleValue(), plotArea.width(), false) + (plotArea.left);
     93         float pixY = ValPixConverter.valToPix(y.doubleValue(), minY.doubleValue(), maxY.doubleValue(), plotArea.height(), true) + plotArea.top;
     94         return new PointF(pixX, pixY);
     95     }
     96 }
     97