Raspberry hello_pi dispmanx.c extended with DrawCircle() for crosshairs demo

dispmanx.c

/*
Copyright (c) 2012, Broadcom Europe Ltd
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of the copyright holder nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

// A simple demo using dispmanx to display an overlay

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>
#include <unistd.h>
#include <sys/time.h>

#include "bcm_host.h"


// from https://github.com/snaptoken/kilo-src/blob/isig/kilo.c
   #include <termios.h>

   struct termios orig_termios;

   void disableRawMode() {
     tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig_termios);
   }

   void enableRawMode() {
     tcgetattr(STDIN_FILENO, &orig_termios);
     atexit(disableRawMode);

     struct termios raw = orig_termios;
     raw.c_lflag &= ~(ECHO | ICANON | ISIG);

     tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw);
   }


#define WIDTH   400
#define HEIGHT  400

#ifndef ALIGN_UP
#define ALIGN_UP(x,y)  ((x + (y)-1) & ~((y)-1))
#endif

typedef struct
{
    DISPMANX_DISPLAY_HANDLE_T   display;
    DISPMANX_MODEINFO_T         info;
    void                       *image;
    DISPMANX_UPDATE_HANDLE_T    update;
    DISPMANX_RESOURCE_HANDLE_T  resource;
    DISPMANX_ELEMENT_HANDLE_T   element;
    uint32_t                    vc_image_ptr;

} RECT_VARS_T;

static RECT_VARS_T  gRectVars;

static void FillRect( VC_IMAGE_TYPE_T type, void *image, int pitch, int aligned_height, int x, int y, int w, int h, int val )
{
    int         row;
    int         col;

    uint32_t *line = (uint32_t *)image + y * (pitch>>2) + x;

    for ( row = 0; row < h; row++ )
    {
        for ( col = 0; col < w; col++ )
        {
            line[col] = val;
        }
        line += (pitch>>2);
    }
}


static void DrawCirc( VC_IMAGE_TYPE_T type, void *image, int pitch, int aligned_height, int x, int y, int r, int val )
{
/* http://rosettacode.org/wiki/Bitmap/Midpoint_circle_algorithm#C
*/
#define plot(x, y) (*((uint32_t *)image + (y) * (pitch>>2) + (x)) = val)
 
void raster_circle(
        unsigned int x0,
        unsigned int y0,
        unsigned int radius)
{
    int f = 1 - radius;
    int ddF_x = 0;
    int ddF_y = -2 * radius;
    int x = 0;
    int y = radius;
 
    plot(x0, y0 + radius);
    plot(x0, y0 - radius);
    plot(x0 + radius, y0);
    plot(x0 - radius, y0);

    while(x < y) 
    {
        if(f >= 0) 
        {
            y--;
            ddF_y += 2;
            f += ddF_y;
        }
        x++;
        ddF_x += 2;
        f += ddF_x + 1;    
        plot(x0 + x, y0 + y);
        plot(x0 - x, y0 + y);
        plot(x0 + x, y0 - y);
        plot(x0 - x, y0 - y);
        plot(x0 + y, y0 + x);
        plot(x0 - y, y0 + x);
        plot(x0 + y, y0 - x);
        plot(x0 - y, y0 - x);
    }
}
#undef plot

    raster_circle(x, y, r);
}


int main(void)
{
    RECT_VARS_T    *vars;
    uint32_t        screen = 0;
    int             ret;
    VC_RECT_T       src_rect;
    VC_RECT_T       dst_rect;
    VC_IMAGE_TYPE_T type = VC_IMAGE_RGBA32;
    int width = WIDTH, height = HEIGHT, X, Y;
    int pitch = ALIGN_UP(width*4, 32);
    int aligned_height = ALIGN_UP(height, 16);
    VC_DISPMANX_ALPHA_T alpha = { DISPMANX_FLAGS_ALPHA_FROM_SOURCE, // | DISPMANX_FLAGS_ALPHA_FIXED_ALL_PIXELS, 
                             120, /*alpha 0->255*/
                             0 };

    vars = &gRectVars;

    bcm_host_init();

    printf("Open display[%i]...\n", screen );
    vars->display = vc_dispmanx_display_open( screen );

    ret = vc_dispmanx_display_get_info( vars->display, &vars->info);
    assert(ret == 0);
    printf( "Display is %d x %d\n", vars->info.width, vars->info.height );

    vars->image = calloc( 1, pitch * height );
    assert(vars->image);

    FillRect( type, vars->image, pitch, aligned_height,         0,          0,     width,     height, 0x00FFFFFF );
    DrawCirc( type, vars->image, pitch, aligned_height,   width/2,   height/2,   width/4,             0xFFFFFFFF );
    DrawCirc( type, vars->image, pitch, aligned_height,   width/2,   height/2, width/4-1,             0xFF000000 );
    FillRect( type, vars->image, pitch, aligned_height,         0,   height/2,     width,          1, 0xFFFFFFFF );
    FillRect( type, vars->image, pitch, aligned_height,         0, 1+height/2,     width,          1, 0xFF000000 );
    FillRect( type, vars->image, pitch, aligned_height,   width/2,          0,         1,     height, 0xFFFFFFFF );
    FillRect( type, vars->image, pitch, aligned_height, 1+width/2,          0,         1,     height, 0xFF000000 );

    vars->resource = vc_dispmanx_resource_create( type,
                                                  width,
                                                  height,
                                                  &vars->vc_image_ptr );
    assert( vars->resource );
    vc_dispmanx_rect_set( &dst_rect, 0, 0, width, height);
    ret = vc_dispmanx_resource_write_data(  vars->resource,
                                            type,
                                            pitch,
                                            vars->image,
                                            &dst_rect );
    assert( ret == 0 );
    vars->update = vc_dispmanx_update_start( 10 );
    assert( vars->update );

    vc_dispmanx_rect_set( &src_rect, 0, 0, width << 16, height << 16 );

    vc_dispmanx_rect_set( &dst_rect, X = ( vars->info.width - width ) / 2,
                                     Y = ( vars->info.height - height ) / 2,
                                     width,
                                     height );

    vars->element = vc_dispmanx_element_add(    vars->update,
                                                vars->display,
                                                2000,               // layer
                                                &dst_rect,
                                                vars->resource,
                                                &src_rect,
                                                DISPMANX_PROTECTION_NONE,
                                                &alpha,
                                                NULL,             // clamp
                                                VC_IMAGE_ROT0 );

    ret = vc_dispmanx_update_submit_sync( vars->update );
    assert( ret == 0 );


{
  enableRawMode();

  char c=0, state=0;
  while (c != 'q') {
   if (read(STDIN_FILENO, &c, 1) == 1) {
    switch (state) {
      case 0: if (c==27) ++state;                break;
      case 1: if (c==91) ++state; else state=0;  break;
      case 2: if (c<65 || c>68) { state=0; break; }
	      switch (c) {
		case 65: --Y; break;
		case 66: ++Y; break;
		case 67: ++X; break;
		case 68: --X; break;
	      }

        // Start a new update, DISPMANX_NO_HANDLE on error
        vars->update = vc_dispmanx_update_start( 10 );
        assert( vars->update );
        assert( vars->update != DISPMANX_NO_HANDLE );

        vc_dispmanx_rect_set( &dst_rect, X,
                                         Y,
                                         width,
                                         height );
        vc_dispmanx_element_change_attributes( vars->update, 
                                               vars->element,
                                               0, //uint32_t change_flags,
                                               3,
                                               9, //uint8_t opacity,
                                               &dst_rect,
                                               &src_rect,
                                               0, //DISPMANX_RESOURCE_HANDLE_T mask,
                                               0); //DISPMANX_TRANSFORM_T transform );
        // End an update and wait for it to complete
        ret = vc_dispmanx_update_submit_sync( vars->update );
	assert( ret == 0 );
    }
    usleep(1000);
   }
  }
}


    ret = vc_dispmanx_element_remove( vars->update, vars->element );
    assert( ret == 0 );
    ret = vc_dispmanx_resource_delete( vars->resource );
    assert( ret == 0 );
    ret = vc_dispmanx_display_close( vars->display );
    assert( ret == 0 );

    return 0;
}

https://www.raspberrypi.org/forums/viewtopic.php?f=33&p=1909146#p1909128

2nd revision, perfect raspivid/raspistill camera preview/aiming crosshairs (overlays camera preview window only on black/white circles/lines, like a mouse cursor):
https://www.raspberrypi.org/forums/viewtopic.php?f=33&t=318902&p=1909183#p1909183