如何从Graphics g获取像素颜色 [英] How to get pixel color from Graphics g
问题描述
在我的学习中，我有图形课程.我们有Bresenham用于画线和画圆.在下一课中，我将学习洪水填充.对于泛洪填充，我需要获取像素颜色以检查是否需要填充. 这是我现在所有课程中的代码.
On my study I have graphics lessons. We have Bresenham for line drawing and Circle drawing. On next lesson I will be learning flood fill. For flood fill I need to get pixel color to check whether I need to fill or not to fill. This is my code now from all lessons.
package lab1;
import javax.swing.*;
import java.awt.*;
import java.util.Random;
public class Lab1 extends JPanel{
private Random random = new Random();
private boolean isRed;
private String s = "";
private int Fill(int x,int y,Graphics g)
{
if ((x < 0) || (y < 0) || (x >= 600) || (y >= 600)) return 0;
return 0;
}
private void drawCircle(int centerX,int centerY,int radius, Graphics g) {
Graphics2D g2d = (Graphics2D) g;
int d = (5 - radius * 4)/4;
int x = 0;
int y = radius;
Color circleColor = Color.white;
do {
g2d.drawRect(centerX + x, centerY + y, 1,1);
g2d.drawRect(centerX + x, centerY - y, 1,1);
g2d.drawRect(centerX - x, centerY + y, 1,1);
g2d.drawRect(centerX - x, centerY - y, 1,1);
g2d.drawRect(centerX + y, centerY + x, 1,1);
g2d.drawRect(centerX + y, centerY - x, 1,1);
g2d.drawRect(centerX - y, centerY + x,1,1);
g2d.drawRect(centerX - y, centerY - x, 1,1);
if (d < 0) {
d += 2 * x + 1;
} else {
d += 2 * (x - y) + 1;
y--;
}
x++;
} while (x <= y);
}
public void line(int x,int y,int x2, int y2, Graphics g) {
Graphics2D g2d = (Graphics2D) g;
//super.paintComponent(g);
int w = x2 - x ;
int h = y2 - y ;
int dx1 = 0, dy1 = 0, dx2 = 0, dy2 = 0 ;
if (w<0) dx1 = -1 ; else if (w>0) dx1 = 1 ;
if (h<0) dy1 = -1 ; else if (h>0) dy1 = 1 ;
if (w<0) dx2 = -1 ; else if (w>0) dx2 = 1 ;
int longest = Math.abs(w) ;
int shortest = Math.abs(h) ;
if (!(longest>shortest)) {
longest = Math.abs(h) ;
shortest = Math.abs(w) ;
if (h<0) dy2 = -1 ; else if (h>0) dy2 = 1 ;
dx2 = 0 ;
}
int numerator = longest >> 1 ;
for (int i=0;i<=longest;i++) {
g2d.drawRect(x, y, 1, 1);
numerator += shortest ;
if (!(numerator<longest)) {
numerator -= longest ;
x += dx1 ;
y += dy1 ;
} else {
x += dx2 ;
y += dy2 ;
}
}
}
public Lab1() {
}
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
drawCircle(100,500,50,g);
drawCircle(500,500,50,g);
g.setColor(Color.red);
line(50,450,550,450,g);
line(50,450,50,350,g);
line(50,350,150,350,g);
line(150,350,325,175,g);
line(325,175,400,175,g);
line(400,175,400,325,g);
line(400,325,550,325,g);
line(550,325,550,450,g);
}
//main method: create an instance of TestPanel and output it on a JFrame
public static void main(String[] args) {
JFrame f = new JFrame();
f.setSize(600, 600);
f.setTitle("Sometimes Red, Sometimes Blue");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(new Lab1());
f.setVisible(true);
}
}
如何从x和y获取像素颜色?
How to get pixel color from x and y ?
推荐答案
您无法从Graphics对象中读取像素.图形是绘图的抽象，可能没有像素(例如打印，绘图等).
You can not read pixels from a Graphics object. Graphics is an abstraction for drawing, there might not be pixels (think of printing, plotting etc.).
您可以创建一个java.awt.BufferedImage并使用其createGraphics()方法获取要渲染的图形，同时能够使用BufferedImage的getRGB()方法读取像素来访问像素.
You can create a java.awt.BufferedImage and use its createGraphics() method to get a Graphics to render into, while being able to read pixels using BufferedImage's getRGB() method to access pixels.
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