JavaMe连载(1)-低级界面绘图之点阵字

【问题描述】JavaMe自带的字体只有三种：Font.SIZE_SMALL、Font.SIZE_MEDIA和Font.SIZE_LARGE，所谓的Font.SIZE_LARGE其实也不是很大。如果要绘制其他字号的字体该怎么办呢？运用低级界面Canvas绘制的点阵字是一个不错的选择。

【字模工具】

晓奇工作室

取模方式：从左到右从上到下，横向8点左高位

【分析】

所谓“点阵字”就是文字是由点阵构成的。点阵字有两个基本属性，那就是宽(width)和高(height)。先看一个例子：

图1 ASCII码取模

如图1所示，Asc5x8表示宽度为5，高度为8的点阵字集。一个char型的字符能表示8位。取模工具实际上是用二进制“1”，表示点阵的文字。用二进制的“0”，表示非文字的空白块。以Asc5x8的“！”为例进行讲解：

0x20,0x20,0x20,0x20,0x20,0x00,0x20,0x00, // -!-

对应的点阵为：

00100000

00100000

00100000

00100000

00100000

00000000

00100000

00000000

注意到，如果将“1”替换为像素点显示，而“0”替换为空白块。则刚好显示为一个“！”号。宽度为5，所以用一个字节表示就可以了。如果宽度超过一个字节，那么如何计算需要多少个字节才能表示宽度呢？原则是，宽度的表示必须为字节的倍数。如宽度为9，那么超过一个字节，所以用2个字节表示。

总结宽度所需字节计算公式如下：

n = (width-1)/8+1

Asc5x8中width即为5.

那么高度如何计算呢？高度其实不用进行计算，由取模软件完成了。

明白上述原理后，就很简单了。且看代码。

 

【代码清单】

package com.token.view.components; import javax.microedition.lcdui.Graphics; import javax.microedition.lcdui.game.GameCanvas; public class CustomFont { public final char font24x48[][] = // ASCII { { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, // - - 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, // -!- 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x00, 0x00,0x78,0x00,0x00,0x78,0x00,0x00,0x78, 0x00,0x00,0x78,0x00,0x00,0x78,0x00,0x00, 0x78,0x00,0x00,0x78,0x00,0x00,0x78,0x00, 0x00,0x78,0x00,0x00,0x78,0x00,0x00,0x30, 0x00,0x00,0x30,0x00,0x00,0x30,0x00,0x00, 0x30,0x00,0x00,0x30,0x00,0x00,0x30,0x00, 0x00,0x30,0x00,0x00,0x30,0x00,0x00,0x30, 0x00,0x00,0x30,0x00,0x00,0x30,0x00,0x00, 0x30,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x70,0x00,0x00,0xF8,0x00,0x00, 0xF8,0x00,0x00,0xF8,0x00,0x00,0x70,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, // -"- 0x00,0x00,0xC0,0xC0,0x01,0xE1,0xE0,0x03, 0xE3,0xE0,0x03,0xC3,0xC0,0x07,0x87,0x80, 0x07,0x07,0x00,0x0E,0x0E,0x00,0x0C,0x0C, 0x00,0x18,0x18,0x00,0x10,0x10,0x00,0x20, 0x20,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, ... { 0x07,0x80,0x00,0x1F,0xC0,0x00,0x10,0xE0, // -- 0x04,0x20,0x70,0x04,0x20,0x38,0x08,0x40, 0x1C,0x08,0x40,0x0F,0x10,0x00,0x07,0xF0, 0x00,0x03,0xC0,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 } }; public CustomFont() { } public void drawmat(GameCanvas canvas, Graphics g, char mat[], int w, int h, int x, int y, int color) { int i,j,k,n; n = (w-1)/8+1; for(j=0; j<h; j++) { for(i=0; i<n; i++) { for(k=0; k<8; k++) { if (!((mat[j * n + i] & (0x80 >> k)) == 0)) /* 测试为1的位则显示 */ { g.setColor(color); g.drawLine(x + i * 8 + k, y + j, x + i * 8 + k, y + j); } } } } } }

n就是表示整个宽度需要的字节数，由于宽度为24，故需要3个字节表示。j记录纵向（高度）位置。代码的处理，就是通过一个画线函数进行的。每次以字节为单位(变量k处理)，对“1”进行检测，检测到1后，记录k的位置。

 

【调用方法】

CustomFont主要用于GameCanvas派生的类。在继承GameCanvas的类中：

(1)声明对象

private CustomFont cf;

(2) 初始化对象(在构造函数中)

cf = new CustomFont();

 

(3) 调用方法(画字符串passwd)

for(int i=0; i<passwd.length(); i++) { cf.drawmat(this, graphics, cf.font24x48[passwd.charAt(i)-' '], 24, 48, (width-6*24)/2+i*24, (height-48)/3, Color.WHITE); }

【效果】

图2中，框中的文字就是通过绘制得到的。

 

图2 实现效果

 

【设计参考】 

(1) http://aiquantong.iteye.com/blog/1457906

(2) http://blog.csdn.net/alleniversoncomputer/article/details/7016368

 

 

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