绘制点网格 [英] Drawing a dot grid

问题描述

我是图形编程的新手.我正在尝试创建一个允许您绘制有向图的程序.首先，我设法绘制了一组矩形(代表节点)，并通过覆盖 Java 中的绘制方法实现了平移和缩放功能.

I'm new to graphics programming. I'm trying to create a program that allows you to draw directed graphs. For a start I have managed to draw a set of rectangles (representing the nodes) and have made pan and zoom capabilities by overriding the paint method in Java.

当节点不多时，这一切似乎都运行良好.我的问题是在尝试绘制点网格时.我一开始使用了一些简单的测试代码，它使用两个嵌套的 for 循环覆盖了一个点网格:

This all seems to work reasonably well while there aren't too many nodes. My problem is when it comes to trying to draw a dot grid. I used a simple bit of test code at first that overlayed a dot grid using two nested for loops:

int iPanX = (int) panX;
int iPanY = (int) panY;
int a = this.figure.getWidth() - iPanX;
int b = this.figure.getHeight() - (int) iPanY;

for (int i = -iPanX; i < a; i += 10) {
    for (int j = -iPanY; j < b; j += 10) {
        g.drawLine(i, j, i, j);
    }
}

这允许我平移网格但不能缩放.然而，平移时的表现很糟糕！我已经做了很多搜索，但我觉得我一定遗漏了一些明显的东西，因为我找不到关于这个主题的任何东西.

This allows me to pan the grid but not zoom. However, the performance when panning is terrible! I've done a lot of searching but I feel that I must be missing something obvious because I can't find anything on the subject.

任何帮助或指示将不胜感激.

Any help or pointers would be greatly appreciated.

--斯蒂芬

推荐答案

对点网格使用 BufferedImage.初始化一次，以后只绘制图像而不是一遍遍地绘制网格.

Use a BufferedImage for the dot grid. Initialize it once and later only paint the image instead of drawing the grid over and over.

private init(){
    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    Graphics g = image.getGraphics();
    // then draw your grid into g
}

public void paint(Graphics g) {
    g.drawImage(image, 0, 0, null);
    // then draw the graphs
}

使用这个很容易实现缩放:

And zooming is easily achieved using this:

g.drawImage(image, 0, 0, null); // so you paint the grid at a 1:1 resolution
Graphics2D g2 = (Graphics2D) g;
g2.scale(zoom, zoom);
// then draw the rest into g2 instead of g

绘制到缩放后的Graphic中会导致线宽等比例变大

Drawing into the zoomed Graphics will lead to proportionally larger line width, etc.

这篇关于绘制点网格的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！