How to display pictures in c++

In C, there are four ways to display images: 1. SDL (cross-platform); 2. Qt (cross-platform framework); 3. OpenCV (image processing and computer vision library); 4. Win32 API (Windows systems). The method chosen depends on the specific situation and application requirements.

How to display images in C

In C, there are several ways to display images:

1. SDL (Simple Direct Media Layer)

SDL is a cross-platform library that supports displaying images on different platforms:

<code class="cpp">#include <SDL2/SDL.h>

int main(int argc, char* argv[]) {
  SDL_Init(SDL_INIT_EVERYTHING);
  SDL_Surface* screen = SDL_SetVideoMode(640, 480, 32, SDL_HWSURFACE);
  SDL_Surface* image = SDL_LoadBMP("image.bmp");
  SDL_BlitSurface(image, NULL, screen, NULL);
  SDL_UpdateWindowSurface(screen);
  SDL_Delay(10000);  // 等待 10 秒
  SDL_Quit();
}</code>

2. Qt

Qt is another cross-platform framework that can display images through the QWidget class:

<code class="cpp">#include <QApplication>
#include <QLabel>
#include <QPixmap>

int main(int argc, char* argv[]) {
  QApplication app(argc, argv);
  QLabel label;
  label.setPixmap(QPixmap("image.png"));
  label.show();
  return app.exec();
}</code>

3. OpenCV (Open Computer Vision Library)

OpenCV focuses on image processing and computer vision, providing functions for displaying images:

<code class="cpp">#include <opencv2/opencv.hpp>

int main(int argc, char* argv[]) {
  cv::Mat image = cv::imread("image.jpg");
  cv::imshow("Image", image);
  cv::waitKey(0);  // 等待用户输入
  return 0;
}</code>

4. Win32 API

In Windows systems, you can Using the Win32 API to display images:

<code class="cpp">#include <windows.h>

int main(int argc, char* argv[]) {
  BITMAP bitmap;
  BITMAPINFO bitmapInfo;
  ZeroMemory(&bitmapInfo, sizeof(bitmapInfo));
  bitmapInfo.bmiHeader.biSize = sizeof(bitmapInfo);
  bitmapInfo.bmiHeader.biWidth = 640;
  bitmapInfo.bmiHeader.biHeight = 480;
  bitmapInfo.bmiHeader.biPlanes = 1;
  bitmapInfo.bmiHeader.biBitCount = 32;
  void* bits;
  HDC hdc = GetDC(NULL);
  HBITMAP hbitmap = CreateDIBSection(hdc, &bitmapInfo, DIB_RGB_COLORS, &bits, NULL, 0);
  HDC hdcMem = CreateCompatibleDC(hdc);
  HGDIOBJ oldObj = SelectObject(hdcMem, hbitmap);
  HBITMAP hbitmapImage = (HBITMAP)LoadImage(NULL, "image.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
  HDC hdcImage = CreateCompatibleDC(hdc);
  HGDIOBJ oldObjImage = SelectObject(hdcImage, hbitmapImage);
  BitBlt(hdcMem, 0, 0, 640, 480, hdcImage, 0, 0, SRCCOPY);
  SelectObject(hdcMem, oldObj);
  SelectObject(hdcImage, oldObjImage);
  DeleteObject(hbitmapImage);
  DeleteObject(hdcImage);
  DeleteDC(hdcMem);
  ReleaseDC(NULL, hdc);
  DeleteObject(hbitmap);
  return 0;
}</code>

Which method you choose depends on the situation and application requirements.

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