十、sdl显示yuv图片
前言
SDL中内置加载BMP的API，使用起来会更加简单，便于初学者学习使用SDL
如果需要加载JPG、PNG等其他格式的图片，可以使用第三方库：SDL_image
测试环境：
- ffmpeg的4.3.2自行编译版本
- windows环境
- qt5.12
- sdl2.0.22（mingw编译器）
显示yuv图片需要知道yuv图片的尺寸和采样格式
ffplay -video_size 564x513 -pixel_format yuv420p out.yuv
完整代码：
SdlShowYuvThread.h
#ifndef SDLSHOWYUVTHREAD_H
#define SDLSHOWYUVTHREAD_H#include <QObject>
#include <QThread>class SdlShowYuvThread : public QThread
{Q_OBJECT
public:explicit SdlShowYuvThread(QObject *parent = nullptr);~SdlShowYuvThread();signals:// QThread interface
protected:virtual void run() override;
};#endif // SDLSHOWYUVTHREAD_H
SdlShowYuvThread.cpp
#include "sdlshowyuvthread.h"#include <SDL2/SDL.h>
#include <QDebug>
#include <QFile>#define END(judge, func) \if (judge) { \qDebug() << #func << "error" << SDL_GetError(); \goto end; \}#define FILENAME "E:/media/picture-test-yuv420p.yuv"
#define PIXEL_FORMAT SDL_PIXELFORMAT_IYUV
#define IMG_W 1928
#define IMG_H 1048SdlShowYuvThread::SdlShowYuvThread(QObject *parent) : QThread(parent)
{// 当监听到线程结束时（finished），就调用deleteLater回收内存connect(this,&SdlShowYuvThread::finished,this,[=](){this->deleteLater();qDebug()<<"SdlShowYuvThread线程结束";});
}SdlShowYuvThread::~SdlShowYuvThread()
{// 断开所有的连接disconnect();// 内存回收之前，正常结束线程requestInterruption();// 安全退出quit();wait();qDebug() << this << "析构（内存被回收）";
}void SdlShowYuvThread::run()
{// 窗口SDL_Window *window = nullptr;// 渲染上下文SDL_Renderer *renderer = nullptr;// 纹理（直接跟特定驱动程序相关的像素数据）SDL_Texture *texture = nullptr;// 文件QFile file(FILENAME);// 初始化子系统END(SDL_Init(SDL_INIT_VIDEO), SDL_Init);// 创建窗口window = SDL_CreateWindow(// 标题"SDL显示YUV图片",// xSDL_WINDOWPOS_UNDEFINED,// ySDL_WINDOWPOS_UNDEFINED,// wIMG_W,// hIMG_H,SDL_WINDOW_SHOWN);END(!window, SDL_CreateWindow);// 创建渲染上下文renderer = SDL_CreateRenderer(window, -1,SDL_RENDERER_ACCELERATED |SDL_RENDERER_PRESENTVSYNC);if (!renderer) {renderer = SDL_CreateRenderer(window, -1, 0);END(!renderer, SDL_CreateRenderer);}// 创建纹理texture = SDL_CreateTexture(renderer,PIXEL_FORMAT,SDL_TEXTUREACCESS_STREAMING,IMG_W, IMG_H);END(!texture, SDL_CreateTexture);// 打开文件if (!file.open(QFile::ReadOnly)) {qDebug() << "file open error" << FILENAME;goto end;}// 将YUV的像素数据填充到textureEND(SDL_UpdateTexture(texture, nullptr, file.readAll().data(), IMG_W),SDL_UpdateTexture);// 设置绘制颜色（画笔颜色）END(SDL_SetRenderDrawColor(renderer,0, 0, 0, SDL_ALPHA_OPAQUE),SDL_SetRenderDrawColor);// 用绘制颜色（画笔颜色）清除渲染目标END(SDL_RenderClear(renderer),SDL_RenderClear);// 拷贝纹理数据到渲染目标（默认是window）END(SDL_RenderCopy(renderer, texture, nullptr, nullptr),SDL_RenderCopy);// 更新所有的渲染操作到屏幕上SDL_RenderPresent(renderer);// 等待退出事件while (!isInterruptionRequested()) {SDL_Event event;SDL_WaitEvent(&event);switch (event.type) {case SDL_QUIT:goto end;}}end:file.close();SDL_DestroyTexture(texture);SDL_DestroyRenderer(renderer);SDL_DestroyWindow(window);SDL_Quit();
}
线程调用：
void MainWindow::on_pushButton_sdl_show_yuv_clicked()
{m_pSdlShowYuvThread=new SdlShowYuvThread(this);m_pSdlShowYuvThread->start();
}
注意：.h文件中提前声明了以下全局变量
SdlShowYuvThread *m_pSdlShowYuvThread=nullptr;
注意：本文为个人记录，新手照搬可能会出现各种问题，请谨慎使用
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