在VGA模式下绘制字符

2023年4月29日 220次阅读

我正在开发一种功能,可以在视频模式下为256 VGA模式绘制字符.

我使用的是6×7字体,其中只包含大写字母,数字和符号.这是数据：

uint8_t  characters[455] = {
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x20,0x20,0x00,0x20,0x00,0x50,
  0x50,0x00,0x00,0x00,0x00,0x00,0x50,0xf8,0x50,0x50,0xf8,0x50,0x00,0x20,0xf8,0xa0,
  0xf8,0x28,0xf8,0x00,0xc8,0xd0,0x20,0x20,0x58,0x98,0x00,0x40,0xa0,0x40,0xa8,0x90,
  0x68,0x00,0x20,0x40,0x00,0x00,0x00,0x00,0x00,0x20,0x40,0x40,0x40,0x40,0x20,0x00,
  0x20,0x10,0x10,0x10,0x10,0x20,0x00,0x50,0x20,0xf8,0x20,0x50,0x00,0x00,0x20,0x20,
  0xf8,0x20,0x20,0x00,0x00,0x00,0x00,0x00,0x60,0x20,0x40,0x00,0x00,0x00,0xf8,0x00,
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x60,0x60,0x00,0x00,0x08,0x10,0x20,0x40,0x80,
  0x00,0x70,0x88,0x98,0xa8,0xc8,0x70,0x00,0x20,0x60,0x20,0x20,0x20,0x70,0x00,0x70,
  0x88,0x08,0x70,0x80,0xf8,0x00,0xf8,0x10,0x30,0x08,0x88,0x70,0x00,0x20,0x40,0x90,
  0x90,0xf8,0x10,0x00,0xf8,0x80,0xf0,0x08,0x88,0x70,0x00,0x70,0x80,0xf0,0x88,0x88,
  0x70,0x00,0xf8,0x08,0x10,0x20,0x20,0x20,0x00,0x70,0x88,0x70,0x88,0x88,0x70,0x00,
  0x70,0x88,0x88,0x78,0x08,0x70,0x00,0x30,0x30,0x00,0x00,0x30,0x30,0x00,0x30,0x30,
  0x00,0x30,0x10,0x20,0x00,0x00,0x10,0x20,0x40,0x20,0x10,0x00,0x00,0xf8,0x00,0xf8,
  0x00,0x00,0x00,0x00,0x20,0x10,0x08,0x10,0x20,0x00,0x70,0x88,0x10,0x20,0x00,0x20,
  0x00,0x70,0x90,0xa8,0xb8,0x80,0x70,0x00,0x70,0x88,0x88,0xf8,0x88,0x88,0x00,0xf0,
  0x88,0xf0,0x88,0x88,0xf0,0x00,0x70,0x88,0x80,0x80,0x88,0x70,0x00,0xe0,0x90,0x88,
  0x88,0x90,0xe0,0x00,0xf8,0x80,0xf0,0x80,0x80,0xf8,0x00,0xf8,0x80,0xf0,0x80,0x80,
  0x80,0x00,0x70,0x88,0x80,0x98,0x88,0x70,0x00,0x88,0x88,0xf8,0x88,0x88,0x88,0x00,
  0x70,0x20,0x20,0x20,0x20,0x70,0x00,0x10,0x10,0x10,0x10,0x90,0x60,0x00,0x90,0xa0,
  0xc0,0xa0,0x90,0x88,0x00,0x80,0x80,0x80,0x80,0x80,0xf8,0x00,0x88,0xd8,0xa8,0x88,
  0x88,0x88,0x00,0x88,0xc8,0xa8,0x98,0x88,0x88,0x00,0x70,0x88,0x88,0x88,0x88,0x70,
  0x00,0xf0,0x88,0x88,0xf0,0x80,0x80,0x00,0x70,0x88,0x88,0xa8,0x98,0x70,0x00,0xf0,
  0x88,0x88,0xf0,0x90,0x88,0x00,0x70,0x80,0x70,0x08,0x88,0x70,0x00,0xf8,0x20,0x20,
  0x20,0x20,0x20,0x00,0x88,0x88,0x88,0x88,0x88,0x70,0x00,0x88,0x88,0x88,0x88,0x50,
  0x20,0x00,0x88,0x88,0x88,0xa8,0xa8,0x50,0x00,0x88,0x50,0x20,0x20,0x50,0x88,0x00,
  0x88,0x50,0x20,0x20,0x20,0x20,0x00,0xf8,0x10,0x20,0x40,0x80,0xf8,0x00,0x60,0x40,
  0x40,0x40,0x40,0x60,0x00,0x00,0x80,0x40,0x20,0x10,0x08,0x00,0x30,0x10,0x10,0x10,
  0x10,0x30,0x00,0x20,0x50,0x88,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xf8,
  0x00,0xf8,0xf8,0xf8,0xf8,0xf8,0xf8};

对于put_char函数,我通过将ascii代码乘以7并减去32来计算数组的偏移量(因为我只使用大写字母).然后我迭代字体大小的宽度和高度(即6和7),如果我找到1则绘制像素,如果找到0则不做任何操作.

void put_char(int x,int y,int ascii_char){
    int l,i,j,h,char_offset;
    j,h,l,i=0;
    char_offset = ascii_char*7-32;
    printf("offset: %d\n",char_offset);
    for (l = 0; l < 7; l++) {
        for (i = 6; i > 0; i--) {
            j++;
            if ((characters[char_offset+l+j] & (1 << i))) { 

                plot_pixel(j+x, h+y, current_color);
            }
        }
        h++;
        j = 0;
    }   
}

但是,我没有在屏幕上正确打印这封信.我想我可能在计算偏移量时遇到问题,但我不知道它在哪里.我也怀疑我的方法来检查数字是1还是0是正确的.任何人都可以帮我解决这个问题吗？

编辑：

这是我得到的图片(注意绘图区域的绿色像素,那些应该是字母’A’

《在VGA模式下绘制字符》

编辑2：

这是我现在变化的图片

 char_offset = ascii_char*7-32;

至

 char_offset = (ascii_char-32)*7;

这几乎是好的,但是’A’的左侧在像素的绘图上有些遗漏.

《在VGA模式下绘制字符》

最佳答案 你很可能想要：

char_offset = (ascii_char-32)*7;

如果先乘以7然后再减去32,那么你将不会减去足够的数量,因为你想要移回32个字符,而不是32像素行.

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