Spresense 用LCD(ILI9341)のフレームバッファにフォントを直接描画

Spresense のカメラアプリケーションを作っていると、フォントを描画したくなりますが、Adafruitのライブラリを使うとフォントがチラつくのが嫌ですよね。

カメラの画像データに直接文字を書き込めれば、チラつかないのに…

と思って作ってみました。AdfruitGFX ライブラリのフォント配列データをそのままパクらせてもらいました。

## Adafruit の ASCII フォント配列データ
Adafruitのフォント配列データです。
```c
// This is the 'classic' fixed-space bitmap font for Adafruit_GFX since 1.0.
// See gfxfont.h for newer custom bitmap font info.

const unsigned char stdfont[] = {
	0x00, 0x00, 0x00, 0x00, 0x00,
	0x3E, 0x5B, 0x4F, 0x5B, 0x3E,
	0x3E, 0x6B, 0x4F, 0x6B, 0x3E,
	0x1C, 0x3E, 0x7C, 0x3E, 0x1C,
	0x18, 0x3C, 0x7E, 0x3C, 0x18,
	0x1C, 0x57, 0x7D, 0x57, 0x1C,
	0x1C, 0x5E, 0x7F, 0x5E, 0x1C,
	0x00, 0x18, 0x3C, 0x18, 0x00,
	0xFF, 0xE7, 0xC3, 0xE7, 0xFF,
	0x00, 0x18, 0x24, 0x18, 0x00,
	0xFF, 0xE7, 0xDB, 0xE7, 0xFF,
	0x30, 0x48, 0x3A, 0x06, 0x0E,
	0x26, 0x29, 0x79, 0x29, 0x26,
	0x40, 0x7F, 0x05, 0x05, 0x07,
	0x40, 0x7F, 0x05, 0x25, 0x3F,
	0x5A, 0x3C, 0xE7, 0x3C, 0x5A,
	0x7F, 0x3E, 0x1C, 0x1C, 0x08,
	0x08, 0x1C, 0x1C, 0x3E, 0x7F,
	0x14, 0x22, 0x7F, 0x22, 0x14,
	0x5F, 0x5F, 0x00, 0x5F, 0x5F,
	0x06, 0x09, 0x7F, 0x01, 0x7F,
	0x00, 0x66, 0x89, 0x95, 0x6A,
	0x60, 0x60, 0x60, 0x60, 0x60,
	0x94, 0xA2, 0xFF, 0xA2, 0x94,
	0x08, 0x04, 0x7E, 0x04, 0x08,
	0x10, 0x20, 0x7E, 0x20, 0x10,
	0x08, 0x08, 0x2A, 0x1C, 0x08,
	0x08, 0x1C, 0x2A, 0x08, 0x08,
	0x1E, 0x10, 0x10, 0x10, 0x10,
	0x0C, 0x1E, 0x0C, 0x1E, 0x0C,
	0x30, 0x38, 0x3E, 0x38, 0x30,
	0x06, 0x0E, 0x3E, 0x0E, 0x06,
	0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x5F, 0x00, 0x00,
	0x00, 0x07, 0x00, 0x07, 0x00,
	0x14, 0x7F, 0x14, 0x7F, 0x14,
	0x24, 0x2A, 0x7F, 0x2A, 0x12,
	0x23, 0x13, 0x08, 0x64, 0x62,
	0x36, 0x49, 0x56, 0x20, 0x50,
	0x00, 0x08, 0x07, 0x03, 0x00,
	0x00, 0x1C, 0x22, 0x41, 0x00,
	0x00, 0x41, 0x22, 0x1C, 0x00,
	0x2A, 0x1C, 0x7F, 0x1C, 0x2A,
	0x08, 0x08, 0x3E, 0x08, 0x08,
	0x00, 0x80, 0x70, 0x30, 0x00,
	0x08, 0x08, 0x08, 0x08, 0x08,
	0x00, 0x00, 0x60, 0x60, 0x00,
	0x20, 0x10, 0x08, 0x04, 0x02,
	0x3E, 0x51, 0x49, 0x45, 0x3E,
	0x00, 0x42, 0x7F, 0x40, 0x00,
	0x72, 0x49, 0x49, 0x49, 0x46,
	0x21, 0x41, 0x49, 0x4D, 0x33,
	0x18, 0x14, 0x12, 0x7F, 0x10,
	0x27, 0x45, 0x45, 0x45, 0x39,
	0x3C, 0x4A, 0x49, 0x49, 0x31,
	0x41, 0x21, 0x11, 0x09, 0x07,
	0x36, 0x49, 0x49, 0x49, 0x36,
	0x46, 0x49, 0x49, 0x29, 0x1E,
	0x00, 0x00, 0x14, 0x00, 0x00,
	0x00, 0x40, 0x34, 0x00, 0x00,
	0x00, 0x08, 0x14, 0x22, 0x41,
	0x14, 0x14, 0x14, 0x14, 0x14,
	0x00, 0x41, 0x22, 0x14, 0x08,
	0x02, 0x01, 0x59, 0x09, 0x06,
	0x3E, 0x41, 0x5D, 0x59, 0x4E,
	0x7C, 0x12, 0x11, 0x12, 0x7C,
	0x7F, 0x49, 0x49, 0x49, 0x36,
	0x3E, 0x41, 0x41, 0x41, 0x22,
	0x7F, 0x41, 0x41, 0x41, 0x3E,
	0x7F, 0x49, 0x49, 0x49, 0x41,
	0x7F, 0x09, 0x09, 0x09, 0x01,
	0x3E, 0x41, 0x41, 0x51, 0x73,
	0x7F, 0x08, 0x08, 0x08, 0x7F,
	0x00, 0x41, 0x7F, 0x41, 0x00,
	0x20, 0x40, 0x41, 0x3F, 0x01,
	0x7F, 0x08, 0x14, 0x22, 0x41,
	0x7F, 0x40, 0x40, 0x40, 0x40,
	0x7F, 0x02, 0x1C, 0x02, 0x7F,
	0x7F, 0x04, 0x08, 0x10, 0x7F,
	0x3E, 0x41, 0x41, 0x41, 0x3E,
	0x7F, 0x09, 0x09, 0x09, 0x06,
	0x3E, 0x41, 0x51, 0x21, 0x5E,
	0x7F, 0x09, 0x19, 0x29, 0x46,
	0x26, 0x49, 0x49, 0x49, 0x32,
	0x03, 0x01, 0x7F, 0x01, 0x03,
	0x3F, 0x40, 0x40, 0x40, 0x3F,
	0x1F, 0x20, 0x40, 0x20, 0x1F,
	0x3F, 0x40, 0x38, 0x40, 0x3F,
	0x63, 0x14, 0x08, 0x14, 0x63,
	0x03, 0x04, 0x78, 0x04, 0x03,
	0x61, 0x59, 0x49, 0x4D, 0x43,
	0x00, 0x7F, 0x41, 0x41, 0x41,
	0x02, 0x04, 0x08, 0x10, 0x20,
	0x00, 0x41, 0x41, 0x41, 0x7F,
	0x04, 0x02, 0x01, 0x02, 0x04,
	0x40, 0x40, 0x40, 0x40, 0x40,
	0x00, 0x03, 0x07, 0x08, 0x00,
	0x20, 0x54, 0x54, 0x78, 0x40,
	0x7F, 0x28, 0x44, 0x44, 0x38,
	0x38, 0x44, 0x44, 0x44, 0x28,
	0x38, 0x44, 0x44, 0x28, 0x7F,
	0x38, 0x54, 0x54, 0x54, 0x18,
	0x00, 0x08, 0x7E, 0x09, 0x02,
	0x18, 0xA4, 0xA4, 0x9C, 0x78,
	0x7F, 0x08, 0x04, 0x04, 0x78,
	0x00, 0x44, 0x7D, 0x40, 0x00,
	0x20, 0x40, 0x40, 0x3D, 0x00,
	0x7F, 0x10, 0x28, 0x44, 0x00,
	0x00, 0x41, 0x7F, 0x40, 0x00,
	0x7C, 0x04, 0x78, 0x04, 0x78,
	0x7C, 0x08, 0x04, 0x04, 0x78,
	0x38, 0x44, 0x44, 0x44, 0x38,
	0xFC, 0x18, 0x24, 0x24, 0x18,
	0x18, 0x24, 0x24, 0x18, 0xFC,
	0x7C, 0x08, 0x04, 0x04, 0x08,
	0x48, 0x54, 0x54, 0x54, 0x24,
	0x04, 0x04, 0x3F, 0x44, 0x24,
	0x3C, 0x40, 0x40, 0x20, 0x7C,
	0x1C, 0x20, 0x40, 0x20, 0x1C,
	0x3C, 0x40, 0x30, 0x40, 0x3C,
	0x44, 0x28, 0x10, 0x28, 0x44,
	0x4C, 0x90, 0x90, 0x90, 0x7C,
	0x44, 0x64, 0x54, 0x4C, 0x44,
	0x00, 0x08, 0x36, 0x41, 0x00,
	0x00, 0x00, 0x77, 0x00, 0x00,
	0x00, 0x41, 0x36, 0x08, 0x00,
	0x02, 0x01, 0x02, 0x04, 0x02,
	0x3C, 0x26, 0x23, 0x26, 0x3C,
	0x1E, 0xA1, 0xA1, 0x61, 0x12,
	0x3A, 0x40, 0x40, 0x20, 0x7A,
	0x38, 0x54, 0x54, 0x55, 0x59,
	0x21, 0x55, 0x55, 0x79, 0x41,
	0x22, 0x54, 0x54, 0x78, 0x42, // a-umlaut
	0x21, 0x55, 0x54, 0x78, 0x40,
	0x20, 0x54, 0x55, 0x79, 0x40,
	0x0C, 0x1E, 0x52, 0x72, 0x12,
	0x39, 0x55, 0x55, 0x55, 0x59,
	0x39, 0x54, 0x54, 0x54, 0x59,
	0x39, 0x55, 0x54, 0x54, 0x58,
	0x00, 0x00, 0x45, 0x7C, 0x41,
	0x00, 0x02, 0x45, 0x7D, 0x42,
	0x00, 0x01, 0x45, 0x7C, 0x40,
	0x7D, 0x12, 0x11, 0x12, 0x7D, // A-umlaut
	0xF0, 0x28, 0x25, 0x28, 0xF0,
	0x7C, 0x54, 0x55, 0x45, 0x00,
	0x20, 0x54, 0x54, 0x7C, 0x54,
	0x7C, 0x0A, 0x09, 0x7F, 0x49,
	0x32, 0x49, 0x49, 0x49, 0x32,
	0x3A, 0x44, 0x44, 0x44, 0x3A, // o-umlaut
	0x32, 0x4A, 0x48, 0x48, 0x30,
	0x3A, 0x41, 0x41, 0x21, 0x7A,
	0x3A, 0x42, 0x40, 0x20, 0x78,
	0x00, 0x9D, 0xA0, 0xA0, 0x7D,
	0x3D, 0x42, 0x42, 0x42, 0x3D, // O-umlaut
	0x3D, 0x40, 0x40, 0x40, 0x3D,
	0x3C, 0x24, 0xFF, 0x24, 0x24,
	0x48, 0x7E, 0x49, 0x43, 0x66,
	0x2B, 0x2F, 0xFC, 0x2F, 0x2B,
	0xFF, 0x09, 0x29, 0xF6, 0x20,
	0xC0, 0x88, 0x7E, 0x09, 0x03,
	0x20, 0x54, 0x54, 0x79, 0x41,
	0x00, 0x00, 0x44, 0x7D, 0x41,
	0x30, 0x48, 0x48, 0x4A, 0x32,
	0x38, 0x40, 0x40, 0x22, 0x7A,
	0x00, 0x7A, 0x0A, 0x0A, 0x72,
	0x7D, 0x0D, 0x19, 0x31, 0x7D,
	0x26, 0x29, 0x29, 0x2F, 0x28,
	0x26, 0x29, 0x29, 0x29, 0x26,
	0x30, 0x48, 0x4D, 0x40, 0x20,
	0x38, 0x08, 0x08, 0x08, 0x08,
	0x08, 0x08, 0x08, 0x08, 0x38,
	0x2F, 0x10, 0xC8, 0xAC, 0xBA,
	0x2F, 0x10, 0x28, 0x34, 0xFA,
	0x00, 0x00, 0x7B, 0x00, 0x00,
	0x08, 0x14, 0x2A, 0x14, 0x22,
	0x22, 0x14, 0x2A, 0x14, 0x08,
	0x55, 0x00, 0x55, 0x00, 0x55, // #176 (25% block) missing in old code
	0xAA, 0x55, 0xAA, 0x55, 0xAA, // 50% block
	0xFF, 0x55, 0xFF, 0x55, 0xFF, // 75% block
	0x00, 0x00, 0x00, 0xFF, 0x00,
	0x10, 0x10, 0x10, 0xFF, 0x00,
	0x14, 0x14, 0x14, 0xFF, 0x00,
	0x10, 0x10, 0xFF, 0x00, 0xFF,
	0x10, 0x10, 0xF0, 0x10, 0xF0,
	0x14, 0x14, 0x14, 0xFC, 0x00,
	0x14, 0x14, 0xF7, 0x00, 0xFF,
	0x00, 0x00, 0xFF, 0x00, 0xFF,
	0x14, 0x14, 0xF4, 0x04, 0xFC,
	0x14, 0x14, 0x17, 0x10, 0x1F,
	0x10, 0x10, 0x1F, 0x10, 0x1F,
	0x14, 0x14, 0x14, 0x1F, 0x00,
	0x10, 0x10, 0x10, 0xF0, 0x00,
	0x00, 0x00, 0x00, 0x1F, 0x10,
	0x10, 0x10, 0x10, 0x1F, 0x10,
	0x10, 0x10, 0x10, 0xF0, 0x10,
	0x00, 0x00, 0x00, 0xFF, 0x10,
	0x10, 0x10, 0x10, 0x10, 0x10,
	0x10, 0x10, 0x10, 0xFF, 0x10,
	0x00, 0x00, 0x00, 0xFF, 0x14,
	0x00, 0x00, 0xFF, 0x00, 0xFF,
	0x00, 0x00, 0x1F, 0x10, 0x17,
	0x00, 0x00, 0xFC, 0x04, 0xF4,
	0x14, 0x14, 0x17, 0x10, 0x17,
	0x14, 0x14, 0xF4, 0x04, 0xF4,
	0x00, 0x00, 0xFF, 0x00, 0xF7,
	0x14, 0x14, 0x14, 0x14, 0x14,
	0x14, 0x14, 0xF7, 0x00, 0xF7,
	0x14, 0x14, 0x14, 0x17, 0x14,
	0x10, 0x10, 0x1F, 0x10, 0x1F,
	0x14, 0x14, 0x14, 0xF4, 0x14,
	0x10, 0x10, 0xF0, 0x10, 0xF0,
	0x00, 0x00, 0x1F, 0x10, 0x1F,
	0x00, 0x00, 0x00, 0x1F, 0x14,
	0x00, 0x00, 0x00, 0xFC, 0x14,
	0x00, 0x00, 0xF0, 0x10, 0xF0,
	0x10, 0x10, 0xFF, 0x10, 0xFF,
	0x14, 0x14, 0x14, 0xFF, 0x14,
	0x10, 0x10, 0x10, 0x1F, 0x00,
	0x00, 0x00, 0x00, 0xF0, 0x10,
	0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
	0xF0, 0xF0, 0xF0, 0xF0, 0xF0,
	0xFF, 0xFF, 0xFF, 0x00, 0x00,
	0x00, 0x00, 0x00, 0xFF, 0xFF,
	0x0F, 0x0F, 0x0F, 0x0F, 0x0F,
	0x38, 0x44, 0x44, 0x38, 0x44,
	0xFC, 0x4A, 0x4A, 0x4A, 0x34, // sharp-s or beta
	0x7E, 0x02, 0x02, 0x06, 0x06,
	0x02, 0x7E, 0x02, 0x7E, 0x02,
	0x63, 0x55, 0x49, 0x41, 0x63,
	0x38, 0x44, 0x44, 0x3C, 0x04,
	0x40, 0x7E, 0x20, 0x1E, 0x20,
	0x06, 0x02, 0x7E, 0x02, 0x02,
	0x99, 0xA5, 0xE7, 0xA5, 0x99,
	0x1C, 0x2A, 0x49, 0x2A, 0x1C,
	0x4C, 0x72, 0x01, 0x72, 0x4C,
	0x30, 0x4A, 0x4D, 0x4D, 0x30,
	0x30, 0x48, 0x78, 0x48, 0x30,
	0xBC, 0x62, 0x5A, 0x46, 0x3D,
	0x3E, 0x49, 0x49, 0x49, 0x00,
	0x7E, 0x01, 0x01, 0x01, 0x7E,
	0x2A, 0x2A, 0x2A, 0x2A, 0x2A,
	0x44, 0x44, 0x5F, 0x44, 0x44,
	0x40, 0x51, 0x4A, 0x44, 0x40,
	0x40, 0x44, 0x4A, 0x51, 0x40,
	0x00, 0x00, 0xFF, 0x01, 0x03,
	0xE0, 0x80, 0xFF, 0x00, 0x00,
	0x08, 0x08, 0x6B, 0x6B, 0x08,
	0x36, 0x12, 0x36, 0x24, 0x36,
	0x06, 0x0F, 0x09, 0x0F, 0x06,
	0x00, 0x00, 0x18, 0x18, 0x00,
	0x00, 0x00, 0x10, 0x10, 0x00,
	0x30, 0x40, 0xFF, 0x01, 0x01,
	0x00, 0x1F, 0x01, 0x01, 0x1E,
	0x00, 0x19, 0x1D, 0x17, 0x12,
	0x00, 0x3C, 0x3C, 0x3C, 0x3C,
	0x00, 0x00, 0x00, 0x00, 0x00  // #255 NBSP
};

```

## 文字列の描画
文字列の描画ルーチンを下記に示します。

```C++
#include "Adafruit_ILI9341.h"

#define TFT_DC  9
#define TFT_CS  10
Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC);

#define SCR_WIDTH 320
#define SCR_HEIGHT 240

extern const unsigned char stdfont[];

uint16_t frame_buf[SCR_WIDTH*SCR_HEIGHT];

void draw_fillrect(uint16_t* buf, int16_t sx, int16_t sy, int16_t w, int16_t h, uint16_t color) {
  if (sx < 0) sx = 0;
  if (sy < 0) sy = 0;
  if (sx + w > SCR_WIDTH) w = SCR_WIDTH - sx;
  if (sy + h > SCR_HEIGHT) h = SCR_HEIGHT - sy;

  for (int y = sy; y < sy + h; ++y) {
    for (int x = sx; x < sx + w; ++x) {
      buf[y*SCR_WIDTH + x] = color;
    }
  }  
}

void draw_char(uint16_t* buf, int16_t x, int16_t y, unsigned char c, uint16_t color, uint16_t bg, uint8_t size_x, uint8_t size_y) {
  if ((x >= SCR_WIDTH)           || // Clip right
      (y >= SCR_HEIGHT)          || // Clip bottom
      ((x + 6*size_x - 1) < 0)   || // Clip left
      ((y + 8*size_y - 1) < 0))     // Clip top
      return;

  if (c >= 176) c++; // Handle 'classic' charset behavior

  for (int8_t i = 0; i < 5; ++i) { // Char bitmap = 5 columns
    uint8_t line = stdfont[c*5 + i];
    for (int8_t j = 0; j < 8; ++j, line >>= 1) {
      if (line & 1) {
        if (size_x == 1 && size_y == 1) {
          buf[(y+j)*SCR_WIDTH + (x+i)] = color;
        } else {
          draw_fillrect(buf, x+i*size_x, y+j*size_y, size_x, size_y, color);
        }
      } else if (bg != color) {
        if (size_x == 1 && size_y == 1) {
          buf[(y+j)*SCR_WIDTH + (x+i)] = bg;
        } else {
          draw_fillrect(buf, x+i*size_x, y+j*size_y, size_x, size_y, bg);
        }
      }
    }
  }

  if (bg != color) { // If opaque, draw vertical line for last column
    if (size_x == 1 && size_y == 1) {
      for (int i = 0; i < 8; ++i) {
        if ((x+5+i) >= SCR_WIDTH) break;
        buf[y*SCR_WIDTH + (x+5+i)] = bg;
      }
    } else {
      if ((x+5*size_x + size_x) < SCR_WIDTH) { 
        draw_fillrect(buf, x+5*size_x, y, size_x, 8*size_y, bg);
      }
    }
  }
}

```

## サンプルプログラム

使い方は少し面倒ですが、縦横のフォントの幅を指定して使います。

```C++
void setup() {
  tft.begin();
  tft.setRotation(3);
  memset(&frame_buf[0], 0, SCR_WIDTH*SCR_HEIGHT*sizeof(uint16_t));

  char hello[] = "Hello World!";
  int font_base_width = 5;
  int scale_x = 1;
  int scale_y = 1;
  for (int n = 0; n < sizeof(hello); ++n) {
    draw_char(frame_buf, 10+n*font_base_width*scale_x, 10, hello[n], ILI9341_YELLOW, ILI9341_BLACK, scale_x, scale_y);
  }
  scale_x = 2;
  for (int n = 0; n < sizeof(hello); ++n) {
    draw_char(frame_buf, 10+n*font_base_width*scale_x, 30, hello[n], ILI9341_BLUE, ILI9341_BLACK, scale_x, scale_y);
  }
  scale_y = 2;
  for (int n = 0; n < sizeof(hello); ++n) {
    draw_char(frame_buf, 10+n*font_base_width*scale_x, 60, hello[n], ILI9341_RED, ILI9341_BLACK, scale_x, scale_y);
  }

  scale_x = 3;
  for (int n = 0; n < sizeof(hello); ++n) {
    draw_char(frame_buf, 10+n*font_base_width*scale_x, 100, hello[n], ILI9341_WHITE, ILI9341_BLACK, scale_x, scale_y);
  }

  scale_y = 3;
  for (int n = 0; n < sizeof(hello); ++n) {
    draw_char(frame_buf, 10+n*font_base_width*scale_x, 140, hello[n], ILI9341_PURPLE, ILI9341_BLACK, scale_x, scale_y);
  }

  scale_x = 4;
  scale_y = 4;
  for (int n = 0; n < sizeof(hello); ++n) {
    draw_char(frame_buf, 10+n*font_base_width*scale_x, 200, hello[n], ILI9341_PINK, ILI9341_BLACK, scale_x, scale_y);
  }

  tft.drawRGBBitmap(0, 0, frame_buf, SCR_WIDTH, SCR_HEIGHT);
  while(1);
}

void loop() {
}
```

出力の結果は次のような感じです。
![DSC02600.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/598183/96613ec4-77eb-6aef-fc06-bbd711381d8e.jpeg)