SDL绘制倾斜水印实例代码

下面是一个简单的SDL绘制倾斜水印的示例代码：

#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <SDL2/SDL_gfxPrimitives.h>

int main(int argc, char* argv[]) {
    SDL_Init(SDL_INIT_VIDEO);

    SDL_Window* window = SDL_CreateWindow("SDL Watermark Example",
                                          SDL_WINDOWPOS_CENTERED,
                                          SDL_WINDOWPOS_CENTERED,
                                          640, 480, SDL_WINDOW_SHOWN);

    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

    // 加载水印图像
    SDL_Surface* watermark = IMG_Load("watermark.png");
    if (!watermark) {
        SDL_Log("Failed to load watermark image: %s", IMG_GetError());
        return -1;
    }

    // 创建目标SDL_Surface对象
    SDL_Surface* target = SDL_CreateRGBSurfaceWithFormat(0, 640, 480, 32, SDL_PIXELFORMAT_RGBA8888);
    if (!target) {
        SDL_Log("Failed to create target surface: %s", SDL_GetError());
        SDL_FreeSurface(watermark);
        return -1;
    }

    // 填充目标SDL_Surface对象为白色背景
    SDL_FillRect(target, NULL, SDL_MapRGB(target->format, 255, 255, 255));

    // 进行旋转、缩放等变换操作
    SDL_Surface* transformed = rotozoomSurface(watermark, 30.0, 1.0, SMOOTHING_ON);
    SDL_Rect dstrect = { 100, 100, transformed->w, transformed->h };

    // 在目标SDL_Surface对象上绘制变换后的水印
    SDL_BlitSurface(transformed, NULL, target, &dstrect);

    // 将目标SDL_Surface对象绘制到屏幕上
    SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, target);
    SDL_RenderCopy(renderer, texture, NULL, NULL);
    SDL_RenderPresent(renderer);

    // 清理资源
    SDL_FreeSurface(watermark);
    SDL_FreeSurface(transformed);
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}

在这个示例代码中，我们使用了SDL_image库来加载水印图像，并使用了SDL_gfx库中的rotozoomSurface函数来进行旋转、缩放等变换操作。最后，我们将变换后的水印绘制到了目标SDL_Surface对象上，并将目标SDL_Surface对象绘制到了屏幕上。