在 VGA 模式下绘制一个字符

Question

我正在开发一种功能，可以在 256 VGA 模式的视频模式下绘制角色。我使用 6x7 字体，该字体集仅包含大写字母、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（因为我只使用大写字母）来计算数组的偏移量。然后我遍历字体大小的宽度和高度（即 6 和 7）以绘制像素，如果我找到 1，如果我找到 0，则什么都不做。

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。我想我在计算偏移量时可能会遇到问题，但我不知道它在哪里。我也怀疑我检查数字是 1 还是 0 的方法是否正确。谁能帮我解决这个问题？

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'

编辑 2：

这是我更改后得到的照片

 char_offset = ascii_char*7-32;

到

 char_offset = (ascii_char-32)*7;

几乎不错，但是 'A' 的左侧在像素绘图中不知何故缺失。

Answer 1

您最有可能想要：

char_offset = (ascii_char-32)*7;

如果您先乘以 7 然后减去 32，那么您减去的量将不够，因为您要向后移动 32 个字符，而不是 32 个像素行。

在 VGA 模式下绘制一个字符

Plotting a char in VGA mode

c

dos

vga