#include <SDL2/SDL.h>#include <SDL2/SDL_image.h>#include <stdbool.h>
typedef unsigned char u8;
#define TITLE "Image Viewer"#define WIDTH 1500#define HEIGHT 900
#define ZOOM_COEFF 0.1
int dpi_w, dpi_h;SDL_Window *window;SDL_Renderer *renderer;
bool init(const char *title, int width, int height) { int res = SDL_Init(SDL_INIT_VIDEO); if (res != 0) { SDL_Log("SDL_Init() failed (%d)", res); return false; }
window = SDL_CreateWindow(title, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_RESIZABLE); if (!window) { SDL_Log("SDL_CreateWindow() failed"); return false; }
float hdpi, vdpi; SDL_GetDisplayDPI(SDL_GetWindowDisplayIndex(window), NULL, &hdpi, &vdpi);
dpi_w = (int)hdpi; dpi_h = (int)vdpi;
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC); if (!renderer) { SDL_Log("SDL_CreateRenderer() failed"); return false; }
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
return true;}
int clamp(int n, int min, int max) { if (n < min) return min; if (n > max && max >= min) return max; return n;}
int main(int argc, char **argv) { if (!init(TITLE, WIDTH, HEIGHT)) return 1;
SDL_Surface *map_sf = IMG_Load(argv[1]); if (!map_sf) return 2;
int map_w = map_sf->w; int map_h = map_sf->h;
SDL_Texture *map = SDL_CreateTextureFromSurface(renderer, map_sf); SDL_FreeSurface(map_sf);
float x = 0, y = 0; float scale = 1.0; float cursor_x = 0, cursor_y = 0;
int click_x = -1, click_y = -1; int prev_mouse_x = -1, prev_mouse_y = -1; bool lmouse = false; bool ctrl = false;
while (true) { bool quit = false; bool lclick = false; bool lrelease = false; int scroll_y = 0;
int mouse_x = -1, mouse_y = -1; SDL_GetMouseState(&mouse_x, &mouse_y);
SDL_Event event; while (!quit && SDL_PollEvent(&event)) { switch (event.type) { case SDL_QUIT: quit = true; break; case SDL_MOUSEBUTTONDOWN: if (event.button.button == SDL_BUTTON_LEFT) { lclick = true; lmouse = true; click_x = mouse_x; click_y = mouse_y; } SDL_CaptureMouse((SDL_bool)true); break; case SDL_MOUSEBUTTONUP: lmouse = false; lrelease = false; SDL_CaptureMouse((SDL_bool)false); break; case SDL_MOUSEWHEEL: scroll_y = event.wheel.y; break; case SDL_KEYDOWN: { SDL_Keycode key = event.key.keysym.sym; if (key == SDLK_LCTRL) ctrl = true; break; } case SDL_KEYUP: { SDL_Keycode key = event.key.keysym.sym; if (key == SDLK_LCTRL) ctrl = false; break; } } } if (quit) break;
int sc_w, sc_h; SDL_GetRendererOutputSize(renderer, &sc_w, &sc_h); int half_sc_w = sc_w / 2; int half_sc_h = sc_h / 2;
if (ctrl) { if (scroll_y != 0) { float coeff = 1.0 + ZOOM_COEFF; if (scroll_y < 0) coeff = 1.0 / coeff;
int cur_x = (mouse_x - half_sc_w) / scale; int cur_y = (mouse_y - half_sc_h) / scale;
scale *= coeff;
x += cur_x - (mouse_x - half_sc_w) / scale; y += cur_y - (mouse_y - half_sc_h) / scale; } if (lmouse && prev_mouse_x >= 0 && prev_mouse_y >= 0) { x += (prev_mouse_x - mouse_x) / scale; y += (prev_mouse_y - mouse_y) / scale; } }
x = clamp(x, 0, map_w); y = clamp(y, 0, map_h);
int scaled_half_w = half_sc_w / scale; int scaled_half_h = half_sc_h / scale; int scaled_w = sc_w / scale; int scaled_h = sc_h / scale; int end_x = map_w - scaled_w; int end_y = map_h - scaled_h;
SDL_Rect src = { x - scaled_half_w, y - scaled_half_h, sc_w / scale, sc_h / scale }; SDL_Rect dst = { 0, 0, sc_w, sc_h };
if (src.x < 0) { dst.x = -src.x * scale; src.x = 0; } if (src.x > end_x) { dst.w = sc_w - (src.x - end_x) * scale; src.w = dst.w / scale; } if (src.y < 0) { dst.y = -src.y * scale; src.y = 0; } if (src.y > end_y) { dst.h = sc_h - (src.y - end_y) * scale; src.h = dst.h / scale; }
SDL_RenderClear(renderer); SDL_RenderCopy(renderer, map, &src, &dst); SDL_RenderPresent(renderer);
prev_mouse_x = mouse_x; prev_mouse_y = mouse_y; }
SDL_DestroyTexture(map); SDL_DestroyRenderer(renderer); SDL_DestroyWindow(window); SDL_Quit(); return 0;}