JavaMe開(kāi)發(fā)：低級(jí)界面繪圖之點(diǎn)陣字

作者：tandesir 2012-05-09 09:49:54

JavaMe自帶的字體只有三種：Font.SIZE_SMALL、Font.SIZE_MEDIA和Font.SIZE_LARGE，所謂的Font.SIZE_LARGE其實(shí)也不是很大。如果要繪制其他字號(hào)的字體該怎么辦呢？運(yùn)用低級(jí)界面Canvas繪制的點(diǎn)陣字是一個(gè)不錯(cuò)的選擇。

【問(wèn)題描述】JavaMe自帶的字體只有三種：Font.SIZE_SMALL、Font.SIZE_MEDIA和Font.SIZE_LARGE，所謂的Font.SIZE_LARGE其實(shí)也不是很大。如果要繪制其他字號(hào)的字體該怎么辦呢？運(yùn)用低級(jí)界面Canvas繪制的點(diǎn)陣字是一個(gè)不錯(cuò)的選擇。

【字模工具】

曉奇工作室

取模方式：從左到右從上到下，橫向8點(diǎn)左高位

【分析】

所謂“點(diǎn)陣字”就是文字是由點(diǎn)陣構(gòu)成的。點(diǎn)陣字有兩個(gè)基本屬性，那就是寬(width)和高(height)。先看一個(gè)例子：

如圖1所示，Asc5x8表示寬度為5，高度為8的點(diǎn)陣字集。一個(gè)char型的字符能表示8位。取模工具實(shí)際上是用二進(jìn)制“1”，表示點(diǎn)陣的文字。用二進(jìn)制的“0”，表示非文字的空白塊。以Asc5x8的“！”為例進(jìn)行講解：

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

對(duì)應(yīng)的點(diǎn)陣為：

00100000

00000000

00100000

00000000

注意到，如果將“1”替換為像素點(diǎn)顯示，而“0”替換為空白塊。則剛好顯示為一個(gè)“！”號(hào)。寬度為5，所以用一個(gè)字節(jié)表示就可以了。如果寬度超過(guò)一個(gè)字節(jié)，那么如何計(jì)算需要多少個(gè)字節(jié)才能表示寬度呢？原則是，寬度的表示必須為字節(jié)的倍數(shù)。如寬度為9，那么超過(guò)一個(gè)字節(jié)，所以用2個(gè)字節(jié)表示。

總結(jié)寬度所需字節(jié)計(jì)算公式如下：

n = (width-1)/8+1

Asc5x8中width即為5.

那么高度如何計(jì)算呢？高度其實(shí)不用進(jìn)行計(jì)算，由取模軟件完成了。

明白上述原理后，就很簡(jiǎn)單了。且看代碼。

【代碼清單】

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)) /* 測(cè)試為1的位則顯示 */    
                             {     
                        g.setColor(color);     
                                    g.drawLine(x + i * 8 + k, y + j, x + i * 8 + k, y + j);     
                                }     
 
                }  
            }  
        }  
    }  
 
}

n就是表示整個(gè)寬度需要的字節(jié)數(shù)，由于寬度為24，故需要3個(gè)字節(jié)表示。j記錄縱向（高度）位置。代碼的處理，就是通過(guò)一個(gè)畫(huà)線函數(shù)進(jìn)行的。每次以字節(jié)為單位(變量k處理)，對(duì)“1”進(jìn)行檢測(cè)，檢測(cè)到1后，記錄k的位置。

【調(diào)用方法】

CustomFont主要用于GameCanvas派生的類(lèi)。在繼承GameCanvas的類(lèi)中：

(1)聲明對(duì)象

private CustomFont cf;

(2) 初始化對(duì)象(在構(gòu)造函數(shù)中)

cf = new CustomFont();

(3) 調(diào)用方法(畫(huà)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);  
}