SDL2 draw a rectangle in an image without window [closed] - c

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Is it possible to draw a rectangle on top of an image without creating a pop up window? I was able to draw a rectangle on top of an image with following code, but I don't want the window to be popped up, is it possible?
What I want is load jpg image -> draw rectangles -> save image as jpg.
int main(int argc, char** argv)
{
bool quit = false;
SDL_Event event;
SDL_Init(SDL_INIT_VIDEO);
IMG_Init(IMG_INIT_JPG);
SDL_Window* window = SDL_CreateWindow("Test",
SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, 0);
SDL_Surface* image = IMG_Load("test.jpg");
if (!image) {
printf("Image NULL\n");
return -1;
}
SDL_Texture* texture = SDL_CreateTexture(renderer,
SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_STATIC,
image->w, image->h);
image = SDL_ConvertSurfaceFormat(image, SDL_PIXELFORMAT_ARGB8888, 0);
while (!quit)
{
SDL_UpdateTexture(texture, NULL, image->pixels,
image->w * sizeof(Uint32));
SDL_WaitEvent(&event);
switch (event.type)
{
case SDL_QUIT:
quit = true;
break;
}
SDL_SetRenderDrawColor(renderer, 136, 8, 8, 255);
SDL_Rect dstrect = { 20, 10, 320, 145};
SDL_RenderCopy(renderer, texture, NULL, NULL);
SDL_RenderDrawRect(renderer, &dstrect);
SDL_RenderPresent(renderer);
}
SDL_DestroyTexture(texture);
SDL_FreeSurface(image);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
IMG_Quit();
SDL_Quit();
return 0;
}

Answer 1

You can use SDL2's software renderer to draw to surface, then save this surface to a file.
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <stdio.h>
#include <stdbool.h>
int main(int argc, char** argv)
{
SDL_Init(SDL_INIT_VIDEO);
IMG_Init(IMG_INIT_JPG);
// load input image
SDL_Surface* image = IMG_Load("test.jpg");
if (!image) {
printf("Image NULL\n");
return -1;
}
// create target surface
SDL_Surface *output_surface = SDL_CreateRGBSurface(0,
image->w, image->h, 32,
0, 0, 0, 0);
// create software renderer that renders to target surface
SDL_Renderer *renderer = SDL_CreateSoftwareRenderer(output_surface);
// create texture from input surface
SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, image);
SDL_SetRenderDrawColor(renderer, 136, 8, 8, 255);
SDL_Rect dstrect = { 20, 10, 320, 145};
SDL_RenderCopy(renderer, texture, NULL, NULL);
SDL_RenderDrawRect(renderer, &dstrect);
SDL_RenderPresent(renderer);
// save target surface to JPEG file
IMG_SaveJPG(output_surface, "test_output.jpg", 90);
SDL_DestroyTexture(texture);
SDL_FreeSurface(image);
SDL_DestroyRenderer(renderer);
SDL_FreeSurface(output_surface);
IMG_Quit();
SDL_Quit();
return 0;
}
Other way would be to create SDL_Surface and use functions like SDL_BlitSurface to copy your image on top of it, and SDL_FillRect to draw filled rectangle (e.g. draw 4 sides of not-filled rectangle).