opengl es 离屏使用的具体例子
时间: 2024-09-28 10:02:07 浏览: 20
OpenGL ES(Elastic OpenGL ES)是一种轻量级版本的OpenGL,适用于移动设备和嵌入式系统。离屏渲染是指将图形绘制到一个Offscreen Buffer(内存缓冲区),而不是直接显示到屏幕上,然后在合适的时候再将缓冲内容复制回屏幕。
一个具体的例子可能是游戏开发中的帧缓冲(Framebuffer Object, FBO)。在游戏中,你可以创建一个FBO,并将背景图、粒子效果等复杂的渲染工作放在这个缓冲上。步骤如下:
1. **创建FBO**:首先,你需要创建一个FBO并绑定,设置其宽度和高度与屏幕一致。
2. **绘制到FBO**:在游戏循环的每一帧,绘制场景元素时,将GL drawing target切换到FBO,而不是默认的屏幕,这样所有的渲染都会进入这个内存缓冲。
3. **存储数据**:绘制完成后,FBO的内容保存在内存中。
4. **复制结果**:当需要更新屏幕时,再将FBO的内容解绑并复制到屏幕缓冲,完成画面刷新。
5. **清理资源**:最后别忘了释放FBO和其他相关资源。
这种技术有助于优化性能,尤其是在处理复杂图形和动画时,因为它允许你在后台进行大量渲染,只在需要的时候将最终结果呈现在用户眼前。
相关问题
OPENGL es MediaCodec例子
这里提供一个使用OpenGL ES和MediaCodec的简单例子,用于解码视频并将其渲染到屏幕上:
```java
public class VideoRenderer implements SurfaceTexture.OnFrameAvailableListener {
private static final String TAG = "VideoRenderer";
private SurfaceTexture mSurfaceTexture;
private Surface mSurface;
private int mTextureId;
private MediaCodec mMediaCodec;
private MediaFormat mMediaFormat;
private ByteBuffer[] mInputBuffers;
private ByteBuffer[] mOutputBuffers;
private int mWidth;
private int mHeight;
private boolean mIsRunning = false;
private EGLDisplay mEGLDisplay;
private EGLSurface mEGLSurface;
private EGLContext mEGLContext;
public VideoRenderer(SurfaceTexture surfaceTexture, int width, int height) {
mSurfaceTexture = surfaceTexture;
mWidth = width;
mHeight = height;
}
public void start(String filePath) throws IOException {
mMediaFormat = MediaFormat.createVideoFormat("video/avc", mWidth, mHeight);
mMediaCodec = MediaCodec.createDecoderByType("video/avc");
mMediaCodec.configure(mMediaFormat, mSurface, null, 0);
mInputBuffers = mMediaCodec.getInputBuffers();
mOutputBuffers = mMediaCodec.getOutputBuffers();
File file = new File(filePath);
FileInputStream inputStream = new FileInputStream(file);
FileChannel fileChannel = inputStream.getChannel();
mMediaCodec.start();
while (mIsRunning) {
int inputBufferIndex = mMediaCodec.dequeueInputBuffer(1000);
if (inputBufferIndex >= 0) {
ByteBuffer inputBuffer = mInputBuffers[inputBufferIndex];
int sampleSize = fileChannel.read(inputBuffer);
if (sampleSize < 0) {
mMediaCodec.queueInputBuffer(inputBufferIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
} else {
mMediaCodec.queueInputBuffer(inputBufferIndex, 0, sampleSize, 0, 0);
}
}
MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
int outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 1000);
while (outputBufferIndex >= 0) {
mMediaCodec.releaseOutputBuffer(outputBufferIndex, true);
outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 0);
}
}
}
public void stop() {
mIsRunning = false;
// Release MediaCodec
if (mMediaCodec != null) {
mMediaCodec.stop();
mMediaCodec.release();
mMediaCodec = null;
}
// Destroy EGL context and surface
if (mEGLDisplay != EGL14.EGL_NO_DISPLAY) {
EGL14.eglMakeCurrent(mEGLDisplay, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_CONTEXT);
if (mEGLSurface != null) {
EGL14.eglDestroySurface(mEGLDisplay, mEGLSurface);
}
if (mEGLContext != null) {
EGL14.eglDestroyContext(mEGLDisplay, mEGLContext);
}
EGL14.eglTerminate(mEGLDisplay);
}
// Release SurfaceTexture and Surface
if (mSurfaceTexture != null) {
mSurfaceTexture.release();
mSurfaceTexture = null;
}
if (mSurface != null) {
mSurface.release();
mSurface = null;
}
}
@Override
public void onFrameAvailable(SurfaceTexture surfaceTexture) {
// Update SurfaceTexture
surfaceTexture.updateTexImage();
// Render frame with OpenGL ES
float[] transformMatrix = new float[16];
surfaceTexture.getTransformMatrix(transformMatrix);
GLES20.glClearColor(0, 0, 0, 1);
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
GLES20.glUseProgram(mProgram);
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, mTextureId);
GLES20.glUniformMatrix4fv(mTransformMatrixHandle, 1, false, transformMatrix, 0);
GLES20.glVertexAttribPointer(mPositionHandle, 2, GLES20.GL_FLOAT, false, 0, mVertexBuffer);
GLES20.glVertexAttribPointer(mTextureHandle, 2, GLES20.GL_FLOAT, false, 0, mTextureBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);
GLES20.glEnableVertexAttribArray(mTextureHandle);
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
GLES20.glDisableVertexAttribArray(mPositionHandle);
GLES20.glDisableVertexAttribArray(mTextureHandle);
// Swap buffers
EGL14.eglSwapBuffers(mEGLDisplay, mEGLSurface);
}
}
```
在这个示例中,我们首先创建一个`SurfaceTexture`和一个`Surface`来将视频渲染到屏幕上。然后,我们创建一个`MediaCodec`来解码视频,并将其配置为使用指定的`Surface`进行输出。我们使用`FileInputStream`和`FileChannel`来从文件中读取视频数据,并将其输入到`MediaCodec`中进行解码。最后,我们使用OpenGL ES将解码后的视频帧渲染到屏幕上。
需要注意的是,在`onFrameAvailable`回调中,我们需要使用OpenGL ES将视频帧渲染到屏幕上,并且需要在渲染完成后调用`EGL14.eglSwapBuffers`来交换前后缓冲区。此外,我们还需要在程序退出时释放所有资源,包括`MediaCodec`,EGL上下文和SurfaceTexture。
使用OpenGL3.0为AVFrame离屏渲染添加水印的完整代码
由于AVFrame和OpenGL在很多方面都是非常复杂的主题,因此为AVFrame添加水印的完整代码可能因情况而异,具体取决于您的环境和需求。不过,我可以提供一个基本的框架,以便您开始尝试在OpenGL 3.0中为AVFrame添加水印。以下是一个简单的例子,它使用OpenGL 3.0为AVFrame离屏渲染添加一个简单的红色矩形:
```c++
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define WIDTH 640
#define HEIGHT 480
GLuint loadShader(const char* source, GLenum shaderType);
GLuint createProgram(const char* vertexShaderSource, const char* fragmentShaderSource);
int main() {
GLFWwindow* window;
if (!glfwInit()) {
std::cerr << "Failed to initialize GLFW" << std::endl;
return -1;
}
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
window = glfwCreateWindow(WIDTH, HEIGHT, "AVFrame Watermarking", NULL, NULL);
if (!window) {
std::cerr << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if (glewInit() != GLEW_OK) {
std::cerr << "Failed to initialize GLEW" << std::endl;
return -1;
}
const GLfloat vertices[] = {
-1.0f, -1.0f,
1.0f, -1.0f,
1.0f, 1.0f,
-1.0f, 1.0f,
};
const GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
GLuint vao, vbo, ebo;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glGenBuffers(1, &ebo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
const char* vertexShaderSource = R"glsl(
#version 300 es
in vec2 position;
void main() {
gl_Position = vec4(position, 0.0, 1.0);
}
)glsl";
const char* fragmentShaderSource = R"glsl(
#version 300 es
precision mediump float;
out vec4 fragColor;
void main() {
fragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
)glsl";
GLuint program = createProgram(vertexShaderSource, fragment
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