Java BufferedImage 使用不需要的背景颜色保存 [英] Java BufferedImage saves with unwanted background color
问题描述
提前感谢您的帮助
说明:该程序绘制、显示和保存图像.它的工作原理如下:对象本身扩展了 Frame.在构造函数中,该对象创建一个 BufferedImage,并调用在该图像上绘制的方法.然后,它将图像显示到框架上.最后,它将图像保存到一个文件中(我不在乎它使用什么格式).主程序创建对象,剩下的由它来做.
Description: The program draws, displays, and saves an image. It works as following: the object itself extends Frame. In the constructor, the object creates a BufferedImage, and calls a method that draw onto that image. Then, it displays the image onto the Frame. Finally, it saves the image into a file (I don't care what format it uses). The main program creates the object, which does the rest.
问题:保存的文件总是有彩色背景!这特别奇怪,因为显示的图像很好.如果我在 ImageIO.write() 中使用jpg"格式,背景会偏红.如果我使用png"格式,背景是深灰色.
Problem: The saved file always has a colored background! This is especially wierd since the displayed image is fine. If I use "jpg" format with ImageIO.write(), the background is reddish. If I use the "png" format, the background is dark grey.
我已经花了一段时间,但我仍然不知道到底发生了什么!
I've spent a while on this, and I still have no idea what the hell is happening!
import java.awt.Frame ;
import java.awt.image.BufferedImage ;
import java.io.IOException ;
import java.awt.event.WindowEvent ;
import java.awt.event.WindowAdapter ;
import java.awt.Toolkit ;
import java.awt.Graphics2D ;
import java.awt.Graphics ;
import java.awt.Color ;
import java.awt.Dimension ;
import javax.imageio.ImageIO ;
import java.io.File ;
import java.awt.geom.Rectangle2D;
public class HGrapher extends Frame{
private BufferedImage img ;
private float colors[][] ; //the colors for every rectangle
private double availWidth ;
private double availHeight ;
public HGrapher(String saveFileName, int numRects) throws IOException {
//*add window closer
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0); }
});
//*get colors to use
setColors( numRects) ;
//*figure out the size of the image and frame
this.availHeight = (3.0/4) * Toolkit.getDefaultToolkit().getScreenSize().height ;
this.availWidth = (3.0/4) * Toolkit.getDefaultToolkit().getScreenSize().width ;
//*create the image
this.img = new BufferedImage( (int)availWidth, (int)availHeight, BufferedImage.TYPE_INT_ARGB);
Graphics2D drawer = img.createGraphics() ;
drawer.setBackground(Color.WHITE);
this.makeImg( drawer) ;
//*display the image
this.setSize( new Dimension( (int)availWidth, (int)availHeight ) ) ;
this.setVisible(true);
//*save the image
ImageIO.write(img, "jpg",new File( (saveFileName +".jpg") ) );
}
//*draws the image by filling rectangles whose color are specified by this.colors
public void makeImg( Graphics2D drawer) {
double rectWidth = this.availWidth / (double)colors.length ;
for(int i = 0 ; i < colors.length ; i ++) {
drawer.setColor( new Color( this.colors[i][0], this.colors[i][1], this.colors[i][2],
this.colors[i][3] ) ) ;
drawer.fill( new Rectangle2D.Double( rectWidth*i, 0, rectWidth, this.availHeight ) ) ;
}
}
//*paint method
public void paint(Graphics g) {
Graphics2D drawer = (Graphics2D)g ;
drawer.drawImage(img, 0, 0, null) ;
}
//*creates an array of the colors rectangles are filled with
public void setColors( int numRects) {
this.colors = new float[ numRects][4] ;
//*make every 1st rect red
for(int i = 0 ; i< colors.length ; i+= 3) {
this.colors[i][0] = (float).8 ; this.colors[i][1] = (float).1 ; this.colors[i][2] = (float).1 ;
this.colors[i][3] = (float).8 ; }
//*make every 2nd rect green
for(int i = 1 ; i< colors.length ; i+= 3) {
this.colors[i][0] = (float).1 ; this.colors[i][1] = (float).8 ; this.colors[i][2] = (float).1 ;
this.colors[i][3] = (float).8 ; }
//*make every 3rd rect
for(int i = 2 ; i< colors.length ; i+= 3) {
this.colors[i][0] = (float).1 ; this.colors[i][1] = (float).1 ; this.colors[i][2] = (float).8 ;
this.colors[i][3] = (float).8 ; }
}
public static void main (String[]args) throws IOException {
HGrapher hg = new HGrapher("saved", 14) ;
}
}
推荐答案
setBackground()
只设置用于清除图像的颜色,并没有真正清除图像.在 setBackground()
之后调用 Graphics.clearRect(int,int,int,int)
.像这样:
setBackground()
only set the Color that is used to clear the image, it does not actually clear the image. Call Graphics.clearRect(int,int,int,int)
after setBackground()
. Like so:
//*create the image
this.img = new BufferedImage( (int)availWidth, (int)availHeight, BufferedImage.TYPE_INT_ARGB);
Graphics2D drawer = img.createGraphics() ;
drawer.setBackground(Color.WHITE);
drawer.clearRect(0,0,(int)availWidth,(int)availHeight);
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