SDL bmp image background - c++

Question

As you can see below there is bmp image but its background color is white:
How can i change it to be for example black (without editing the bmp image itself)?
Here I have code to show bmp image on window:
#include <iostream>
#include "SDL.h"
using namespace std;
int main(int argc, char *args[])
{
SDL_Window *window = nullptr;
SDL_Renderer *renderer = nullptr;
SDL_Surface *surface = nullptr;
SDL_Texture *texture = nullptr;
SDL_Event event;
SDL_Rect positionRect;
SDL_Rect dimensionRect;
positionRect.x = 0;
positionRect.y = 0;
positionRect.w = 100;
positionRect.h = 100;
dimensionRect.x = 0;
dimensionRect.y = 0;
dimensionRect.w = 300;
dimensionRect.h = 300;
if (SDL_Init(SDL_INIT_EVERYTHING) < 0) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't initialize SDL: %s", SDL_GetError());
return 1;
}
if (SDL_CreateWindowAndRenderer(500, 500, SDL_WINDOW_OPENGL, &window, &renderer)) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create window and renderer: %s", SDL_GetError());
return 1;
}
surface = SDL_LoadBMP("sample.bmp");
if (!surface) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create surface from image: %s", SDL_GetError());
return 1;
}
texture = SDL_CreateTextureFromSurface(renderer, surface);
if (!texture) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create texture from surface: %s", SDL_GetError());
return 1;
}
SDL_FreeSurface(surface);
surface = nullptr;
while (1) {
SDL_PollEvent(&event);
if (event.type == SDL_QUIT) {
break;
}
//SDL_SetRenderDrawColor(renderer, 0xff000000, 0x00ff0000, 0x0000ff00, 0x000000ff);
SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0x00);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture, &positionRect, &dimensionRect);
SDL_RenderPresent(renderer);
}
SDL_DestroyTexture(texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}

Answer 1

You should add these 2 lines,
Uint32 colorkey = SDL_MapRGB(surface->format, 255, 255, 255);
SDL_SetColorKey(surface, SDL_TRUE, colorkey);
before this line in your code
texture = SDL_CreateTextureFromSurface(renderer, surface);