Line-graph drawable
/**
*
* LibSparkline : a free Java sparkline chart library
*
*
* Project Info: http://reporting.pentaho.org/libsparkline/
*
* (C) Copyright 2008, by Larry Ogrodnek, Pentaho Corporation and Contributors.
*
* This library is free software; you can redistribute it and/or modify it under the terms
* of the Apache License 2.0.
*
* This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* You should have received a copy of the Apache License 2.0 along with this library;
* if not, a online version is available at http://www.apache.org/licenses/
*
* [Java is a trademark or registered trademark of Sun Microsystems, Inc.
* in the United States and other countries.]
*
* ------------
* LineGraphDrawable.java
* ------------
*/
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.geom.Line2D;
import java.awt.geom.Rectangle2D;
/**
* A very fast and very simple line-graph drawable. This code is based on the
* LineGraph class writen by Larry Ogrodnek but instead of producing a
* low-resolution image, this class writes the content into a Graphics2D
* context.
*
* @author Thomas Morgner
*/
public class LineGraphDrawable {
private static final int DEFAULT_SPACING = 2;
private int spacing;
private Color color;
private Color background;
private Number[] data;
/**
* Creates a default bargraph drawable with some sensible default colors and
* spacings.
*/
public LineGraphDrawable() {
this.color = Color.black;
this.spacing = DEFAULT_SPACING;
}
/**
* Returns the numeric data for the drawable or null, if the drawable has no
* data.
*
* @return the data.
*/
public Number[] getData() {
return data;
}
/**
* Defines the numeric data for the drawable or null, if the drawable has no
* data.
*
* @param data
* the data (can be null).
*/
public void setData(final Number[] data) {
this.data = data;
}
/**
* Returns the main color for the bars.
*
* @return the main color for the bars, never null.
*/
public Color getColor() {
return color;
}
/**
* Defines the main color for the bars.
*
* @param color
* the main color for the bars, never null.
*/
public void setColor(final Color color) {
if (color == null) {
throw new NullPointerException();
}
this.color = color;
}
/**
* Returns the color for the background of the graph. This property can be
* null, in which case the bar will have a transparent background.
*
* @return color for the background or null, if the graph has a transparent
* background color.
*/
public Color getBackground() {
return background;
}
/**
* Defines the color for the background of the graph. This property can be
* null, in which case the bar will have a transparent background.
*
* @param background
* the background or null, if the graph has a transparent background
* color.
*/
public void setBackground(final Color background) {
this.background = background;
}
/**
* Returns the spacing between the bars.
*
* @return the spacing between the bars.
*/
public int getSpacing() {
return spacing;
}
/**
* Defines the spacing between the bars.
*
* @param spacing
* the spacing between the bars.
*/
public void setSpacing(final int spacing) {
this.spacing = spacing;
}
/**
* Draws the bar-graph into the given Graphics2D context in the given area.
* This method will not draw a graph if the data given is null or empty.
*
* @param graphics
* the graphics context on which the bargraph should be rendered.
* @param drawArea
* the area on which the bargraph should be drawn.
*/
public void draw(final Graphics2D graphics, final Rectangle2D drawArea) {
if (graphics == null) {
throw new NullPointerException();
}
if (drawArea == null) {
throw new NullPointerException();
}
final int height = (int) drawArea.getHeight();
if (height <= 0) {
return;
}
final Graphics2D g2 = (Graphics2D) graphics.create();
if (background != null) {
g2.setPaint(background);
g2.draw(drawArea);
}
if (data == null || data.length == 0) {
g2.dispose();
return;
}
g2.translate(drawArea.getX(), drawArea.getY());
float d = getDivisor(data, height);
final int spacing = getSpacing();
final int w = (((int) drawArea.getWidth()) - (spacing * (data.length - 1))) / (data.length - 1);
float min = Float.MAX_VALUE;
for (int index = 0; index < data.length; index++) {
Number i = data[index];
if (i == null) {
continue;
}
final float value = i.floatValue();
if (value < min) {
min = value;
}
}
int x = 0;
int y = -1;
if (d == 0.0) {
// special case -- a horizontal straight line
d = 1.0f;
y = -height / 2;
}
final Line2D.Double line = new Line2D.Double();
for (int i = 0; i < data.length - 1; i++) {
final int px1 = x;
x += (w + spacing);
final int px2 = x;
g2.setPaint(color);
final Number number = data[i];
final Number nextNumber = data[i + 1];
if (number == null && nextNumber == null) {
final float delta = height - ((0 - min) / d);
line.setLine(px1, y + delta, px2, y + delta);
} else if (number == null) {
line.setLine(px1, y + (height - ((0 - min) / d)), px2, y
+ (height - ((nextNumber.floatValue() - min) / d)));
} else if (nextNumber == null) {
line.setLine(px1, y + (height - ((number.floatValue() - min) / d)), px2, y
+ (height - ((0 - min) / d)));
} else {
line.setLine(px1, y + (height - ((number.floatValue() - min) / d)), px2, y
+ (height - ((nextNumber.floatValue() - min) / d)));
}
g2.draw(line);
}
g2.dispose();
}
/**
* Computes the scale factor to scale the given numeric data into the target
* height.
*
* @param data
* the numeric data.
* @param height
* the target height of the graph.
* @return the scale factor.
*/
public static float getDivisor(final Number[] data, final int height) {
if (data == null) {
throw new NullPointerException("Data array must not be null.");
}
if (height < 1) {
throw new IndexOutOfBoundsException("Height must be greater or equal to 1");
}
float max = Float.MIN_VALUE;
float min = Float.MAX_VALUE;
for (int index = 0; index < data.length; index++) {
Number i = data[index];
if (i == null) {
continue;
}
final float numValue = i.floatValue();
if (numValue < min) {
min = numValue;
}
if (numValue > max) {
max = numValue;
}
}
if (max <= min) {
return 1.0f;
}
if (height == 1) {
return 0;
}
return (max - min) / (height - 1);
}
}
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