利用freetype生成显示数据的简单示例

使用linux fb进行界面显示时，遇到文字（英文、中文、其他语言、符号等），需要先将这些字符转换成图像，再进行显示。freetype是一个比较通用的转换工具。

这里先给出一个简单的使用示例：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include FT_FREETYPE_H


/*****************************************************************************
 *
 * Macro definition
 *
 *****************************************************************************/
#define FU_IMAGE_MARGIN                 (2)


/*****************************************************************************
 *
 * Structure/Class Definition
 *
 *****************************************************************************/


/*****************************************************************************
 *
 * Data definition
 *
 *****************************************************************************/
static FT_Library library;
static FT_Face face;

static FT_GlyphSlot slot;
static FT_Matrix matrix; /* transformation matrix */
static FT_Vector pen;    /* untransformed origin  */

// 每英寸像素个数，根据480*800屏幕计算得到235
static uint32_t pixel_per_inch;
static uint32_t canvas_max_width;
static uint32_t canvas_max_height;
static uint8_t **canvas_buf;

//
static pthread_mutex_t text_trans_mutext;



/*****************************************************************************
 *
 * Function Entity
 *
 *****************************************************************************/
static void DrawBitmap(FT_Bitmap *bitmap, FT_Int x, FT_Int y)
{
    FT_Int i;
    FT_Int j;
    FT_Int p;
    FT_Int q;
    FT_Int x_max = x + bitmap->width;
    FT_Int y_max = y + bitmap->rows;

    //
    q = (FT_Int)0 - (FT_Int)(bitmap->width);
    for (j = y; j < y_max; j ++) {

        q += bitmap->width;
        for (i = x, p = 0; i < x_max; i ++, p ++) {

            if (i < 0 || j < 0 || i >= canvas_max_width || j >= canvas_max_height) {
                continue;
            }

            canvas_buf[j][i] |= bitmap->buffer[q + p];
        }
    }
}


static void GetBitmap(int image_width, int image_height, uint8_t *image, int *real_width, int *real_height) {
    int x;
    int y;
    int none_zero_x_start = canvas_max_width;
    int none_zero_x_end = 0;
    int none_zero_y_start = canvas_max_height;
    int none_zero_y_end = 0;
    uint8_t *line;

    //
    *real_width = 0;
    *real_height = 0;


    /* 
    // 得到字符点阵的顶部y坐标
    for (y = 0; y < canvas_max_height; ++ y) {
        for (x = 0; x < canvas_max_width; ++ x) {

            if (canvas_buf[y][x] != 0)  {
                none_zero_y_start = y;
                break;
            }
        }
        if (x < canvas_max_height) break;
    }

    //printf("none_zero_y_start = %d\n\r", none_zero_y_start);

    // 得到字符点阵的底部y坐标
    for (y = canvas_max_height - 1; y >= 0; -- y) {
        for (x = 0; x < canvas_max_width; ++ x) {

            if (canvas_buf[y][x] != 0)  {
                none_zero_y_end = y;
                break;
            }
        }
        if (x < canvas_max_height) break;
    }

    //printf("none_zero_y_end = %d\n\r", none_zero_y_end);

    // 得到字符点阵的左边x坐标
    for (x = 0; x < canvas_max_width; ++ x) {
        for (y = 0; y < canvas_max_height; ++ y) {

            if (canvas_buf[y][x] != 0) {
                none_zero_x_start = x;
                break;
            }
        }
        if (y < canvas_max_height) break;
    }

    //printf("none_zero_x_start = %d\n\r", none_zero_x_start);

    // 得到字符点阵的右边x坐标
    for (x = canvas_max_width - 1; x >= 0 ; -- x) {
        for (y = 0; y < canvas_max_height; ++ y) {

            if (canvas_buf[y][x] != 0) {
                none_zero_x_end = x;
                break;
            }
        }
        if (y < canvas_max_height) break;
    }

    //printf("none_zero_x_end = %d\n\r", none_zero_x_end);
    */
    for (x = 0; x < canvas_max_width; ++ x) {
        for (y = 0; y < canvas_max_height; ++ y) {

            if (canvas_buf[y][x] != 0) {
                if (none_zero_x_start > x) none_zero_x_start = x;
                if (none_zero_x_end < x) none_zero_x_end = x;
                if (none_zero_y_start > y) none_zero_y_start = y;
                if (none_zero_y_end < y) none_zero_y_end = y;
            }
        }
    }


    //
    (*real_width) = none_zero_x_end - none_zero_x_start + 1 + (FU_IMAGE_MARGIN << 1);
    if ((*real_width) > image_width) (*real_width) = image_width;
    
    *real_height = none_zero_y_end - none_zero_y_start + 1 + (FU_IMAGE_MARGIN << 1);
    if (*real_height > image_height) *real_height = image_height;

    //printf("real_height = %d, real_width = %d\n\r", *real_height, *real_width);

    //
    for (y = 0; y < *real_height && y < image_height; ++ y) {
            line = image + (y + FU_IMAGE_MARGIN) * (*real_width);
            //printf("image = %p, line = %p, y = %d\n\r", line, image, y);
        for (x = 0; x < *real_width && x < (*real_width); ++ x) {
            line[x + FU_IMAGE_MARGIN] = canvas_buf[y + none_zero_y_start][x + none_zero_x_start];
        }
    }
}

/* 
static void show_image(void)
{
    int i, j;

    for (i = 0; i < canvas_max_height; i++)
    {
        printf("%d:", i);
        for (j = 0; j < canvas_max_width; j++)
            putchar(canvas_buf[i][j] == 0 ? '.'
                                     : canvas_buf[i][j] < 128 ? '+'
                                                         : '*');
        putchar('\n');
    }
}
*/



int FreetypeInit(const char *font_file, uint32_t ppi, uint32_t max_width, uint32_t max_height) {

    int err;
    int i;

    // initialize library
    err = FT_Init_FreeType(&library);
    if (err) {
        printf("Init library failed\n\r");
        return -1;
    }


    // create face object
    err = FT_New_Face(library, font_file, 0, &face);
    if (err == FT_Err_Unknown_File_Format) {
        printf("the font is not supported\n\r");
        return -1;
    } else if (err) {
        printf("the font file can't open\n\r");
        return -1;
    }


    //
    pixel_per_inch = ppi;
    canvas_max_width = max_width;
    canvas_max_height = max_height;

    canvas_buf = (uint8_t **)malloc(max_height * sizeof(uint8_t *));
    if (NULL == canvas_buf) {
        printf("malloc canvas buf fail\n\r");
        FreetypeExit();
        return -1;
    }

    memset(canvas_buf, 0, max_height * sizeof(uint8_t *));
    for (i = 0; i < max_height; ++ i) {
        canvas_buf[i] = (uint8_t *)malloc(max_width);
        if (NULL == canvas_buf[i]) {
            printf("malloc canvas buf fail\n\r");
            FreetypeExit();
            return -1;
        }
    }


    //
    pthread_mutex_init(&text_trans_mutext, NULL);


    return 0;
}


void FreetypeExit(void) {
    int i;

    FT_Done_Face(face);
    FT_Done_FreeType(library);

    if (canvas_buf) {
        for (i = 0; i < canvas_max_height; ++ i) {
            if (canvas_buf[i]) {
                free(canvas_buf[i]);
                canvas_buf[i] = 0;
            }
        }

        free(canvas_buf);
        canvas_buf = NULL;
    }


    pthread_mutex_destroy(&text_trans_mutext);
}



// 文字转换完成的点阵信息，连续的存储在缓存区域里，由返回的宽、高信息，说明如何从缓存区域读取点阵数据
// 返回的点阵信息，按如下存储，image[height][width]
//
// 0        -       *real_width
// 
// |
// 
// * real_height
// 
int GetCharacterStringBitmap(const wchar_t *char_str, int font_size, int image_width, int image_height, 
                             uint8_t *image, int *real_width, int * real_height) {

    int i;
    //double angle = 0;
    int rtn;


    // 
    rtn = 0;
    pthread_mutex_lock(&text_trans_mutext);



    // set character size
    //rtn = FT_Set_Char_Size(face, font_size * 64, 0, pixel_per_inch, 0);
    rtn = FT_Set_Char_Size(face, font_size << 6, 0, pixel_per_inch, 0);
    if (rtn != 0) {
        printf("FT_Set_Char_Size error\n");
        goto ERR_OUT;
    }

    // cmap selection
    //FT_Select_Charmap(face, FT_ENCODING_GB2312);

    //
    for (i = 0; i < canvas_max_height; ++ i) {
        memset(canvas_buf[i], 0, canvas_max_width);
    }

    //
    slot = face->glyph;


    // set up matrix
    /* 
    matrix.xx = (cos(angle) * 0x10000L);
    matrix.xy = (-sin(angle) * 0x10000L);
    matrix.yx = (sin(angle) * 0x10000L);
    matrix.yy = (cos(angle) * 0x10000L);
    */
    /* 
    */
    matrix.xx = (FT_Fixed)(0x10000L);//(cos(angle) * 0x10000L);
    matrix.xy = (FT_Fixed)(0L);//(-sin(angle) * 0x10000L);
    matrix.yx = (FT_Fixed)(0L);//(sin(angle) * 0x10000L);
    matrix.yy = (FT_Fixed)(0x10000L);//(cos(angle) * 0x10000L);

    //
    //pen.x = 0 * 64;
    //pen.y = (canvas_max_height / 2) * 64;
    pen.x = 0;//0 * 64;
    pen.y = canvas_max_height << 5;//(canvas_max_height / 2) * 64;


    for (i = 0; char_str[i] != '\0'; ++ i) {
        FT_Set_Transform(face, &matrix, &pen);
        rtn = FT_Load_Char(face, char_str[i], FT_LOAD_RENDER);
        if (rtn != 0) {
            printf("FT_load_char error, i = %d\n", i);
            goto ERR_OUT;
        }

        DrawBitmap(&slot->bitmap,
                    slot->bitmap_left,
                    canvas_max_height - slot->bitmap_top);

        // increment pen position
        pen.x += slot->advance.x;
        pen.y += slot->advance.y;
    }

    //show_image();


    GetBitmap(image_width, image_height, image, real_width, real_height);
    rtn = 0;


ERR_OUT:
    pthread_mutex_unlock(&text_trans_mutext);

    return rtn;
}

下面这个例子，是利用前面封装的函数，实现多行文字转换成图像。里面调用的函数，都在本博客的tslib、freetype相关文章中给出过：

#include 
#include 
#include 
#include 
#include 
#include  
#include 
#include 



/*****************************************************************************
 *
 * Macro definition
 *
 *****************************************************************************/
#define GR_MAX_TEXT_LINE                (8)

// position
#define GB_UI_ALIGN_VERTICAL_MASK               (0x0f)
#define GB_UI_ALIGN_VERTICAL_TOP                (1 << 0)
#define GB_UI_ALIGN_VERTICAL_BOTTOM             (1 << 1)
#define GB_UI_ALIGN_VERTICAL_CENTER             (GB_UI_ALIGN_VERTICAL_TOP | GB_UI_ALIGN_VERTICAL_BOTTOM)

#define GB_UI_ALIGN_HORIZONTAL_MASK             (0xf0)
#define GB_UI_ALIGN_HORIZONTAL_LEFT             (1 << 4)
#define GB_UI_ALIGN_HORIZONTAL_RIGHT            (1 << 5)
#define GB_UI_ALIGN_HORIZONTAL_CENTER           (GB_UI_ALIGN_HORIZONTAL_LEFT | GB_UI_ALIGN_HORIZONTAL_RIGHT)


/*****************************************************************************
 *
 * Structure/Class Definition
 *
 *****************************************************************************/


/*****************************************************************************
 *
 * Data definition
 *
 *****************************************************************************/


/*****************************************************************************
 *
 * Function Entity
 *
 *****************************************************************************/

//
int GuiText2Image(const wchar_t *char_str, int font_size, uint32_t row_spacing, uint32_t text_align, int width, 
                  uint8_t **text_image, int32_t *text_image_width, int32_t *text_image_height) {

    wchar_t             *char_tmp;
    wchar_t             *char_buf[GR_MAX_TEXT_LINE];
    uint8_t             *image_buf[GR_MAX_TEXT_LINE];
    int                 image_width[GR_MAX_TEXT_LINE];
    int                 image_height[GR_MAX_TEXT_LINE];
    uint8_t             *image_line;
    int                 i;
    int                 j;
    int                 l;
    int                 line;
    int                 line_num;
    int                 pre_zero_num;
    int                 suf_zero_num;
    int                 max_width;
    int                 final_height;
    int                 wchar_len;
    int                 rtn;



    rtn = -1;
    wchar_len = wcslen(char_str);


    //
    memset(char_buf, 0, GR_MAX_TEXT_LINE * sizeof(wchar_t *));
    memset(image_buf, 0, GR_MAX_TEXT_LINE * sizeof(uint8_t *));

    // 申请缓存区
    for (i = 0; i < GR_MAX_TEXT_LINE; ++ i) {

        //
        char_buf[i] = (wchar_t *)malloc((wchar_len + 4) * sizeof(wchar_t));
        if (char_buf[i] == NULL) {
            goto ERR_OUT;
        }
        memset(char_buf[i], 0, (wchar_len + 4) * sizeof(wchar_t));

        //
        image_buf[i] = (uint8_t *)malloc(width * width);
        if (image_buf[i] == NULL) {
            goto ERR_OUT;
        }
        memset(image_buf[i], 0, width * width);
    }

    // 
    *text_image = (uint8_t *)malloc(width * width);
    if (NULL == *text_image) {
        goto ERR_OUT;
    }


    // 根据换行，拆分成多个字符串，每行一个字符串
    for (char_tmp = (wchar_t *)char_str, line_num = 0; *char_tmp != '\0' && line_num < GR_MAX_TEXT_LINE; ++ line_num) {
        // 跳过前面的换行符
        while (*char_tmp == '\n' || *char_tmp == '\r') {
            char_tmp ++;
        }

        for (i = 0; *char_tmp != '\n' && *char_tmp != '\r' && *char_tmp != '\0'; ++ i, ++ char_tmp) {
            char_buf[line_num][i] = *char_tmp;
        }

        char_buf[line_num][i] = '\0';
    }

    if (0 == line_num) {
        goto ERR_OUT;
    }



    // 每行转换成位图
    for (i = 0, max_width = 0, final_height = 0; i < line_num; ++ i) {

        rtn = GetCharacterStringBitmap(char_buf[i], font_size, width, width, 
                                       image_buf[i], &(image_width[i]), &(image_height[i]));

        if (image_width[i] > max_width) {
            max_width = image_width[i];
        }
        final_height += image_height[i];
    }
    // 加上行距
    final_height += ((line_num - 1) * row_spacing);




    // 按对齐方式，合并每行的位图
    // 高度，每行的高度相加
    // 宽度，找到最宽的。然后按对齐方式，拷贝每行的位图到最终buf
    for (line = 0, l = 0; line < line_num; ++ line) {
        switch (text_align & GB_UI_ALIGN_HORIZONTAL_MASK)
        {
        case GB_UI_ALIGN_HORIZONTAL_LEFT:
            pre_zero_num = 0;
            suf_zero_num = max_width - image_width[line];
            break;

        case GB_UI_ALIGN_HORIZONTAL_RIGHT:
            pre_zero_num = max_width - image_width[line];
            suf_zero_num = 0;
            break;

        case GB_UI_ALIGN_HORIZONTAL_CENTER:
            pre_zero_num = (max_width - image_width[line]) / 2;
            suf_zero_num = max_width - image_width[line] - pre_zero_num;
            break;
        
        default:
            pre_zero_num = 0;
            suf_zero_num = max_width - image_width[line];
            break;
        }


        // 开始拷贝数据
        for (j = 0; j < image_height[line]; ++ j) {
            image_line = image_buf[line] + image_width[line] * j;

            // 根据分析结果，补每行前面的0
            for (i = 0; i < pre_zero_num; ++ i) {
                (*text_image)[l ++] = 0;
            }
            // 拷贝数据
            for (i = 0; i < image_width[line]; ++ i) {
                (*text_image)[l ++] = image_line[i];
            }

            // 根据分析结果，补每行后面的0
            for (i = 0; i < suf_zero_num; ++ i) {
                (*text_image)[l ++] = 0;
            }
        }

        // 每2行间增加行距，最后一行下面不增加行距
        if ((line + 1) < line_num) {
            for (j = 0; j < (int)row_spacing; ++ j) {
                for (i = 0; i < max_width; ++ i) {
                    (*text_image)[l ++] = 0;
                }
            }
        }
    }

    *text_image_width  = max_width;
    *text_image_height = final_height;


    rtn = 0; 


ERR_OUT:
    for (i = 0; i < GR_MAX_TEXT_LINE; i ++) {
        if (char_buf[i]) {
            free(char_buf[i]);
        }

        if(image_buf[i]) {
            free(image_buf[i]);
        }
    }

    return rtn;
}