Image Scaling and DPI

1#include <SDL.h>
2#include <SDL_image.h>
3#include <iostream>
4
DPI Scale Helper|Show
5float GetDPIScale(SDL_Window* Window) {/*...*/}
12
13class Sprite {
14  SDL_Surface* Image;
15  int BaseWidth;
16  int BaseHeight;
17
18public:
19  Sprite(const char* Path) {
20    Image = IMG_Load(Path);
21    BaseWidth = Image->w;
22    BaseHeight = Image->h;
23  }
24
25  void Draw(SDL_Surface* Target,
26    int x, int y, float Scale
27  ) {
28    SDL_Rect Dest{
29      x,
30      y,
31      int(BaseWidth * Scale),
32      int(BaseHeight * Scale)
33    };
34    SDL_BlitScaled(Image, nullptr, Target, &Dest);
35  }
36
37  ~Sprite() {
38    SDL_FreeSurface(Image);
39  }
40};

1class MultiResSprite {
2  std::vector<SDL_Surface*> Images;
3  std::vector<float> Scales{
4    1.0f, 1.5f, 2.0f, 4.0f};
5  int BaseWidth;
6  int BaseHeight;
7
8public:
9  MultiResSprite(
10    const std::vector<const char*>& Paths) {
11    for (auto Path : Paths) {
12      Images.push_back(IMG_Load(Path));
13    }
14    BaseWidth = Images[0]->w;
15    BaseHeight = Images[0]->h;
16  }
17
18  void Draw(
19    SDL_Surface* Target,
20    int x, int y, float Scale
21  ) {
22    // Find best matching image
23    size_t Best{0};
24    float BestDiff{std::abs(Scales[0] - Scale)};
25
26    for (size_t i = 1; i < Scales.size(); ++i) {
27      float Diff{std::abs(Scales[i] - Scale)};
28      if (Diff < BestDiff) {
29        Best = i;
30        BestDiff = Diff;
31      }
32    }
33
34    SDL_Rect Dest{
35      x, y,
36      int(BaseWidth * Scale),
37      int(BaseHeight * Scale)
38    };
39    SDL_BlitScaled(
40      Images[Best], nullptr, Target, &Dest);
41  }
42
43  ~MultiResSprite() {
44    for (auto Image : Images) {
45      SDL_FreeSurface(Image);
46    }
47  }
48};