mediamtx/internal/protocols/rpicamera/exe/text.c

#include <time.h>

#include <ft2build.h>
#include FT_FREETYPE_H

#include "text_font.h"
#include "text.h"

static char errbuf[256];

static void set_error(const char *format, ...) {
    va_list args;
    va_start(args, format);
    vsnprintf(errbuf, 256, format, args);
}

const char *text_get_error() {
    return errbuf;
}

typedef struct {
    bool enabled;
    char *text_overlay;
    FT_Library library;
    FT_Face face;
} text_priv_t;

bool text_create(const parameters_t *params, text_t **text) {
    *text = malloc(sizeof(text_priv_t));
    text_priv_t *textp = (text_priv_t *)(*text);
    memset(textp, 0, sizeof(text_priv_t));

    textp->enabled = params->text_overlay_enable;
    textp->text_overlay = strdup(params->text_overlay);

    if (textp->enabled) {
        int error = FT_Init_FreeType(&textp->library);
        if (error) {
            set_error("FT_Init_FreeType() failed");
            goto failed;
        }

        error = FT_New_Memory_Face(
            textp->library,
            text_font_ttf,
            sizeof(text_font_ttf),
            0,
            &textp->face);
        if (error) {
            set_error("FT_New_Memory_Face() failed");
            goto failed;
        }

        error = FT_Set_Pixel_Sizes(
            textp->face,
            25,
            25);
        if (error) {
            set_error("FT_Set_Pixel_Sizes() failed");
            goto failed;
        }
    }

    return true;

failed:
    free(textp);

    return false;
}

static void draw_rect(uint8_t *buf, int stride, int height, int x, int y, unsigned int rect_width, unsigned int rect_height) {
    uint8_t *Y = buf;
    uint8_t *U = Y + stride * height;
    uint8_t *V = U + (stride / 2) * (height / 2);
    const uint8_t color[3] = {0, 128, 128};
    uint32_t opacity = 45;

    for (unsigned int src_y = 0; src_y < rect_height; src_y++) {
        for (unsigned int src_x = 0; src_x < rect_width; src_x++) {
            unsigned int dest_x = x + src_x;
            unsigned int dest_y = y + src_y;
            int i1 = dest_y*stride + dest_x;
            int i2 = dest_y/2*stride/2 + dest_x/2;

            Y[i1] = ((color[0] * opacity) + (uint32_t)Y[i1] * (255 - opacity)) / 255;
            U[i2] = ((color[1] * opacity) + (uint32_t)U[i2] * (255 - opacity)) / 255;
            V[i2] = ((color[2] * opacity) + (uint32_t)V[i2] * (255 - opacity)) / 255;
        }
    }
}

static void draw_bitmap(uint8_t *buf, int stride, int height, const FT_Bitmap *bitmap, int x, int y) {
    uint8_t *Y = buf;
    uint8_t *U = Y + stride * height;
    uint8_t *V = U + (stride / 2) * (height / 2);

    for (unsigned int src_y = 0; src_y < bitmap->rows; src_y++) {
        for (unsigned int src_x = 0; src_x < bitmap->width; src_x++) {
            uint8_t v = bitmap->buffer[src_y*bitmap->pitch + src_x];

            if (v != 0) {
                unsigned int dest_x = x + src_x;
                unsigned int dest_y = y + src_y;
                int i1 = dest_y*stride + dest_x;
                int i2 = dest_y/2*stride/2 + dest_x/2;
                uint32_t opacity = (uint32_t)v;

                Y[i1] = (uint8_t)(((uint32_t)v * opacity + (uint32_t)Y[i1] * (255 - opacity)) / 255);
                U[i2] = (uint8_t)((128 * opacity + (uint32_t)U[i2] * (255 - opacity)) / 255);
                V[i2] = (uint8_t)((128 * opacity + (uint32_t)V[i2] * (255 - opacity)) / 255);
            }
        }
    }
}

static int get_text_width(FT_Face face, const char *text) {
    int ret = 0;

    for (const char *ptr = text; *ptr != 0x00; ptr++) {
        int error = FT_Load_Char(face, *ptr, FT_LOAD_RENDER);
        if (error) {
            continue;
        }

        ret += face->glyph->advance.x >> 6;
    }

    return ret;
}

void text_draw(text_t *text, uint8_t *buf, int stride, int height) {
    text_priv_t *textp = (text_priv_t *)text;

    if (textp->enabled) {
        time_t timer = time(NULL);
        struct tm *tm_info = localtime(&timer);
        char buffer[255];
        memset(buffer, 0, sizeof(buffer));
        strftime(buffer, 255, textp->text_overlay, tm_info);

        draw_rect(
            buf,
            stride,
            height,
            7,
            7,
            get_text_width(textp->face, buffer) + 10,
            34);

        int x = 12;
        int y = 33;

        for (const char *ptr = buffer; *ptr != 0x00; ptr++) {
            int error = FT_Load_Char(textp->face, *ptr, FT_LOAD_RENDER);
            if (error) {
                continue;
            }

            draw_bitmap(
                buf,
                stride,
                height,
                &textp->face->glyph->bitmap,
                x + textp->face->glyph->bitmap_left,
                y - textp->face->glyph->bitmap_top);

            x += textp->face->glyph->advance.x >> 6;
        }
    }
}