经过大量的研究和挖掘，我找到了glReadPixels的解决方案，以及如何使用PBO来缓冲图像/帧以供以后处理。
因此，我们需要做的第一件事是在GLES2中公开一个额外的函数。在您的应用程序模块中添加一个名为cpp的新目录，然后创建一个名为GlesHelper的新c文件(或者您想要调用它的任何东西)
并粘贴以下代码：
代码语言：javascript运行复制#include
#include
JNIEXPORT void JNICALL
// Change
Java_com_your_full_package_name_helper_GlesHelper_glReadPixels(JNIEnv *env, jobject instance, jint x,
jint y, jint width, jint height,
jint format, jint type) {
// TODO
glReadPixels(x, y, width, height, format, type, 0);
}然后，我们需要向您的项目的根添加一个CMakeFile。右键单击，新文件，输入CMakeLists.txt
并粘贴以下代码
代码语言：javascript运行复制cmake_minimum_required(VERSION 3.4.1)
add_library( # Specifies the name of the library.
native-lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
src/main//cpp//GlesHelper.c )
target_link_libraries( # Specifies the target library.
native-lib
# Links the target library to the log library
# included in the NDK.
${log-lib}
GLESv2)现在打开您的应用程序/模块build.gradle文件
将其粘贴到Gradle文件的android.defaultConfig部分
代码语言：javascript运行复制externalNativeBuild {
// Encapsulates your CMake build configurations.
cmake {
// Provides a relative path to your CMake build script.
cppFlags "-std=c++11 -fexceptions"
arguments "-DANDROID_STL=c++_shared"
}
}然后将其粘贴到Gradle文件的android部分
代码语言：javascript运行复制externalNativeBuild {
// Encapsulates your CMake build configurations.
cmake {
// Provides a relative path to your CMake build script.
path "CMakeLists.txt"
}
}所以这就是所有的MakeFile和c的东西--所有的设置--让我们转到一些java上
在项目中创建一个与c文件(即com_your_full_package_name_helper = com.your.full.package.name.helper )中的包匹配的新文件
确保这些匹配正确，类名和函数名相同。
所以你的课应该是这样
代码语言：javascript运行复制package com.your.full.package.name.helper;
public class GlesHelper
{
public static native void glReadPixels(int x, int y, int width, int height, int format, int type);
}因为我们已经将本机代码添加到项目中，所以我们需要使用System.loadLibrary(“本机库”)来加载我们的新方法。
在启动下一位之前，将这些成员变量添加到您的渲染器中
代码语言：javascript运行复制/**
* The PBO Ids, increase the allocate amount for more PBO's
* The more PBO's the smoother the frame rate (to an extent)
* Side affect of having more PBO's the frames you get from the PBO's will lag behind by the amount of pbo's
*/
private IntBuffer mPboIds = IntBuffer.allocate(2);;
/**
* The current PBO Index
*/
private int mCurrentPboIndex = 0;
/**
* The next PBO Index
*/
private int mNextPboIndex = 1;所以现在我们需要初始化我们的PBO--这很简单
代码语言：javascript运行复制 // Generate the buffers for the pbo's
GLES30.glGenBuffers(mPboIds.capacity(), mPboIds);
// Loop for how many pbo's we have
for (int i = 0; i < mPboIds.capacity(); i++)
{
// Bind the Pixel_Pack_Buffer to the current pbo id
GLES30.glBindBuffer(GLES30.GL_PIXEL_PACK_BUFFER, mPboIds.get(i));
// Buffer empty data, capacity is the width * height * 4
GLES30.glBufferData(GLES30.GL_PIXEL_PACK_BUFFER, capacity, null, GLES30.GL_STATIC_READ);
}
// Reset the current buffer so we can draw properly
GLES30.glBindBuffer(GLES30.GL_PIXEL_PACK_BUFFER, 0);然后，在开始绘制调用此方法之前，这将将像素数据读入pbo，交换缓冲区，并允许您访问像素数据。
代码语言：javascript运行复制/**
* Reads the pixels from the PBO and swaps the buffers
*/
private void readPixelsFromPBO()
{
// Bind the current buffer
GLES30.glBindBuffer(GLES30.GL_PIXEL_PACK_BUFFER, mPboIds.get(mCurrentPboIndex));
// Read pixels into the bound buffer
GlesHelper.glReadPixels(0, 0, mViewWidth, mViewHeight, GLES20.GL_RGBA, GLES30.GL_UNSIGNED_BYTE);
// Bind the next buffer
GLES30.glBindBuffer(GLES30.GL_PIXEL_PACK_BUFFER, mPboIds.get(mNextPboIndex));
// Map to buffer to a byte buffer, this is our pixel data
ByteBuffer pixelsBuffer = (ByteBuffer) GLES30.glMapBufferRange(GLES30.GL_PIXEL_PACK_BUFFER, 0, mViewWidth * mViewHeight * 4, GLES30.GL_MAP_READ_BIT);
if(mSkipFirstFrame)
{
// Skip the first frame as the PBO's have nothing in them until the second render cycle
}
// Set skip first frame to true so we can begin frame processing
mSkipFirstFrame = true;
// Swap the buffer index
mCurrentPboIndex = (mCurrentPboIndex + 1) % mPboIds.capacity();
mNextPboIndex = (mNextPboIndex + 1) % mPboIds.capacity();
// Unmap the buffers
GLES30.glUnmapBuffer(GLES30.GL_PIXEL_PACK_BUFFER);
GLES30.glBindBuffer(GLES30.GL_PIXEL_PACK_BUFFER, GLES20.GL_NONE);
GLES30.glBindFramebuffer(GLES30.GL_FRAMEBUFFER, GLES20.GL_NONE);
}回到我最初的问题，我们的Redner/onDrawMethod会是这样的。
代码语言：javascript运行复制 // Use the OpenGL Program for rendering
GLES20.glUseProgram(mProgram);
// If the Texture Matrix is not null
if (textureMatrix != null)
{
// Apply the Matrix
GLES20.glUniformMatrix4fv(mTexMatrixLoc, 1, false, textureMatrix, 0);
}
// Apply the Matrix
GLES20.glUniformMatrix4fv(mMVPMatrixLoc, 1, false, mMvpMatrix, 0);
// Bind the Texture
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textureID);
// Draw the texture
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, GLConstants.VERTEX_NUM);
// Unbind the Texture
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, 0);
// Read from PBO
readPixelsFromPBO()我希望这能帮助那些在使用glReadPixels的性能上遇到类似问题的人，或者至少是努力实现PBO的人。