要使用Direct Texture,需要有一份android系统的源码部分C++代码如下：#include <stdio.h>#include <stdlib.h>#include <GLES2/gl2.h>#include <GLES2/gl2ext.h>#include <EGL/egl.h>#include <EGL/eglext.h>#include <android/native_window.h>#include <ui/GraphicBuffer.h>#include <dlfcn.h>#include <jni.h>#include "render_native.h"int Graphics::initGL(){
const char* const driver_absolute_path = "/system/lib/egl/libEGL_mali.so";
// On Gingerbread you have to load symbols manually from Mali driver because
// Android EGL library has a bug.
// From ICE CREAM SANDWICH you can freely use the eglGetProcAddress function.
// You might be able to get away with just eglGetProcAddress (no dlopen). Tr y it, else revert to the following code
void* dso = dlopen(driver_absolute_path, RTLD_LAZY);
if (dso != 0)
{
LOGI("dlopen: SUCCEEDED");
_eglCreateImageKHR = (PFNEGLCREATEIMAGEKHRPROC)dlsym(dso, "eglCreateImageKHR");
_eglDestroyImageKHR = (PFNEGLDESTROYIMAGEKHRPROC) dlsym(dso,"eglDestroyImageKHR");
}
else
{
LOGI("dlopen: FAILED! Loading functions in common way!");
_eglCreateImageKHR = (PFNEGLCREATEIMAGEKHRPROC) eglGetProcAddress("eglCreateImageKHR");
_eglDestroyImageKHR = (PFNEGLDESTROYIMAGEKHRPROC) eglGetProcAddress("eglDestroyImageKHR");
}
if(_eglCreateImageKHR == NULL)
{
LOGE("Error: Failed to find eglCreateImageKHR at %s:%in", __FILE__, __LINE__);
exit(1);
}
if(_eglDestroyImageKHR == NULL)
{
LOGE("Error: Failed to find eglDestroyImageKHR at %s:%in", __FILE__, __LINE__);
exit(1);
}
_glEGLImageTargetTexture2DOES = (PFNGLEGLIMAGETARGETTEXTURE2DOESPROC) eglGetProcAddress("glEGLImageTargetTexture2DOES");
if(_glEGLImageTargetTexture2DOES == NULL)
{
LOGI("Error: Failed to find glEGLImageTargetTexture2DOES at %s:%in", __FILE__, __LINE__);
return 0;
}
graphicBuffer = new GraphicBuffer( emu_width,emu_height,
HAL_PIXEL_FORMAT_RGBA_8888,
GraphicBuffer::USAGE_HW_TEXTURE |
GraphicBuffer::USAGE_HW_2D |
GRALLOC_USAGE_SW_READ_OFTEN |
GRALLOC_USAGE_SW_WRITE_OFTEN);
status_t err = graphicBuffer->initCheck();
if (err != NO_ERROR)
{
LOGI("Error: %sn", strerror(-err));
return 0;
}
GGLSurface t;
// graphicBuffer->lock(GraphicBuffer::USAGE_SW_WRITE_OFTEN, &addr);
graphicBuffer->lock(&t, GRALLOC_USAGE_SW_WRITE_OFTEN);
memset(t.data,128,t.stride*t.height);
graphicBuffer->unlock();
// Retrieve andorid native buffer
android_native_buffer_t* anb =graphicBuffer->getNativeBuffer();
// create the new EGLImageKHR
const EGLint attrs[] =
{
EGL_IMAGE_PRESERVED_KHR, EGL_TRUE,
EGL_NONE, EGL_NONE
};
mEngine.mTexture.pEGLImage = _eglCreateImageKHR(eglGetCurrentDisplay(),
mEngine.nContext, EGL_NATIVE_BUFFER_ANDROID, (EGLClientBuffer)anb, attrs);
if(mEngine.mTexture.pEGLImage == EGL_NO_IMAGE_KHR)
{
LOGI("Error: eglCreateImage() failed at %s:%in", __FILE__, __LINE__);
return 0;
}
checkGlError("eglCreateImageKHR");
LOGI("create Program.......");
GLuint gProgram = createProgram(vertex_source, fragment_source);
checkGlError("createProgram");
if (!gProgram) {
LOGE("Could not create program.");
return false;
}
glUseProgram(gProgram);
vPosition = glGetAttribLocation(gProgram, "glVertex");
checkGlError("glGetAttribLocation glVertex");
glEnableVertexAttribArray(vPosition);
a_texCoord0 = glGetAttribLocation(gProgram, "a_texCoord0");
checkGlError("glGetAttribLocation texCoord0");
glEnableVertexAttribArray(a_texCoord0);
s_tex0 = glGetUniformLocation(gProgram, "s_texture0");
checkGlError("glGetAttribLocation texture");
LOGI("glGen Textures.......");
glGenTextures(1, &texID);
glDisable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
glDisable(GL_STENCIL_TEST);
glDisable(GL_DITHER);
checkGlError("glDisable");
// glEnable(GL_TEXTURE_2D);// checkGlError("glEnable(GL_TEXTURE_2D)"); glGenTextures(1,&texID);
checkGlError("glGenTextures");
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texID);
// glPixelStorei(GL_PACK_ALIGNMENT, 1);// glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
// glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, mEngine.mTexture.nTextureWidth, mEngine.mTexture.nTextureHeight, 0,GL_RGBA, GL_UNSIGNED_BYTE, NULL); // glFinish(); _glEGLImageTargetTexture2DOES(GL_TEXTURE_2D,mEngine.mTexture.pEGLImage);
float w = float(emu_width) / float(mEngine.mTexture.nTextureWidth);
float h = float(emu_height) / float(mEngine.mTexture.nTextureHeight);
g_pos=initFloatBuffer(vertices,12);
g_texvbo=initFloatBuffer(texCoords,8);
glViewport(0, 0, mEngine.nScreen_Width, mEngine.nScreen_Height);
return 1;
}void Graphics::renderFrame() {
// texture=(unsigned char*)ture; glClearColor(0.5f, 0.5f, 0.5f, 1);
glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
glUniform1i(s_tex0, 0);
glBindBuffer(GL_ARRAY_BUFFER, g_pos);
glVertexAttribPointer(vPosition, 3, GL_FLOAT, GL_FALSE, 0, 0);
glBindBuffer(GL_ARRAY_BUFFER, g_texvbo);
glVertexAttribPointer(a_texCoord0, 2, GL_FLOAT, GL_FALSE, 0, 0);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
eglSwapBuffers(mEngine.nDisplay, mEngine.nSurface);
｝
void* Graphics::begin(){
GGLSurface t;
graphicBuffer->lock(&t,GRALLOC_USAGE_SW_WRITE_OFTEN);
return t.data;
}void Graphics::end(){
graphicBuffer->unlock();
renderFrame();
}使用时如下：Graphics render;void *buffer=render.begin();
把数据填充到buffer里render.end();编译时包含头文件LOCAL_C_INCLUDES += $(ANDROID_SRC_HOME)/frameworks/base/core/jni/android/graphics
$(ANDROID_SRC_HOME)/frameworks/base/include/
$(ANDROID_SRC_HOME)/hardware/libhardware/include
$(ANDROID_SRC_HOME)/system/core/include
$(ANDROID_SRC_HOME)/frameworks/base/native/include/
$(ANDROID_SRC_HOME)/frameworks/base/opengl/include/
链接选项：LOCAL_LDLIBS := -llog -lGLESv2 -lEGL -landroid -lui -landroid_runtime -ljnigraphicsandroid Opengles 里虽然没有PBO, 但是用Direct Texture能实现类似的功能。direct textures 的使用介绍http://snorp.net/2011/12/16/android-direct-texture.html
eglCreateImageKHR扩展的介绍http://www.khronos.org/registry/egl/extensions/KHR/EGL_KHR_image_base.txt
描述：在opengles 编程时如果用glTexImage2D /glTexSubImage2D API的话，当渲染的图片很大时，速度会变得很慢的，因为运行时会发生数据拷贝的过程，而使用opengles 的扩展glEGLImageTargetTexture2DOES可以解决这个问题，用这个扩展要用到另一个扩展 eglCreateImageKHR 。