Loading and Displaying Images

Handling Different Image Resolutions

How do I handle different image resolutions for various screen sizes?

Abstract art representing computer programming

Handling different image resolutions for various screen sizes is a common challenge in game development. Here's a practical approach using SDL2.

Scaling Images

One way to handle different resolutions is to scale your images at runtime. You can use SDL_BlitScaled() instead of SDL_BlitSurface() to achieve this. Here's how you might modify our Image class to support scaling:

#include <SDL.h>

#include <iostream>
#include <string>

class Image {
public:
  Image(std::string File,
        SDL_PixelFormat* PreferredFormat =
          nullptr)
    : ImageSurface{SDL_LoadBMP(File.c_str())} {
    // Constructor code remains the same
  }

  void Render(SDL_Surface* DestinationSurface,
              SDL_Rect* DestRect = nullptr) {
    SDL_BlitScaled(ImageSurface, nullptr,
                   DestinationSurface,
                   DestRect); 
  }

  // Rest of the class remains unchanged
};

int main() {
  SDL_Init(SDL_INIT_VIDEO);
  SDL_Window* window = SDL_CreateWindow(
    "Scaled Image", SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED, 800, 600, 0);
  SDL_Surface* screenSurface =
    SDL_GetWindowSurface(window);

  Image img{
    "example.bmp", screenSurface->format};

  // Scale to half the window size
  SDL_Rect destRect{0, 0, 400, 300};
  
  img.Render(screenSurface, &destRect);

  SDL_UpdateWindowSurface(window);
  SDL_Delay(5000);

  SDL_DestroyWindow(window);
  SDL_Quit();
  return 0;
}

Responsive Design

For a more responsive approach, you can calculate the scaling factor based on the screen size:

float scaleX = static_cast<float>(screenWidth) /
  originalImageWidth;
float scaleY = static_cast<float>(screenHeight)
  / originalImageHeight;
float scale = std::min(scaleX, scaleY);
// Maintain aspect ratio

int newWidth = static_cast<int>(
  originalImageWidth * scale);
int newHeight = static_cast<int>(
  originalImageHeight * scale);

SDL_Rect destRect{
  // Center horizontally
  (screenWidth - newWidth) / 2,
  // Center vertically
  (screenHeight - newHeight) / 2,
  newWidth, newHeight};

This approach scales the image to fit the screen while maintaining its aspect ratio.

Remember, scaling images at runtime can be computationally expensive. For better performance, consider pre-scaling your images for common resolutions and loading the appropriate one at runtime.

Answers to questions are automatically generated and may not have been reviewed.

sdl2-promo.jpg
Part of the course:

Game Dev with SDL2

Learn C++ and SDL development by creating hands on, practical projects inspired by classic retro games

Free, unlimited access

This course includes:

  • 51 Lessons
  • 100+ Code Samples
  • 91% Positive Reviews
  • Regularly Updated
  • Help and FAQ
Free, Unlimited Access

Professional C++

Comprehensive course covering advanced concepts, and how to use them on large-scale projects.

Screenshot from Warhammer: Total War
Screenshot from Tomb Raider
Screenshot from Jedi: Fallen Order
Contact|Privacy Policy|Terms of Use
Copyright © 2024 - All Rights Reserved