http://blog.csdn.net/sunnytina/article/details/51895406

Android使用Direct Textures提高glReadPixels、glTexImage2D性能 http://www.jianshu.com/p/1fa36461fc6f

Android中的EGL扩展 http://ju.outofmemory.cn/entry/146313

Using the EGL* Image Extension

The conventional way to copy an image into a texture is with either the glTexImage2D() orglTexSubImage2D() methods, but these methods are slow because of how they convert the format of the image data as it is copied. These are really intended for loading static images, not dynamic ones. Moving images between OpenGL* ES textures and another graphics API quickly requires direct access to the memory in which the texture image is stored. Ideally, the image should be copied by an accelerated 2D BitBlt, but that requires the physical address of the image. Otherwise, you can use amemcpy() method instead, which only requires the virtual address of the image.

The EGL* image extension is an extension to the EGL* standard defined by the Khronos Group that provides the virtual or physical addresses of an OpenGL* ES texture. With these addresses, images can be copied to or from OpenGL* ES textures quickly. This technique is so fast that it is possible to stream uncompressed video into OpenGL* ES, but doing so typically requires converting the pixels from the YUV to RGB color space, which is beyond the scope of this article.

The official name of the EGL* image extension is GL_OES_EGL_image. It is widely supported on most platforms, including Android. To confirm which extensions are available on any platform, use the functions provided in Listing 4 to return strings that list all of the available extensions by name for your OpenGL* ES and EGL* drivers.

Listing 4. Checking for available OpenGL* ES and EGL* extensions

glGetString(GL_EXTENSIONS);
eglQueryString(eglGetCurrentDisplay(), EGL_EXTENSIONS);

The header file eglext.h defines the names of the rendering surface types that the EGL* and OpenGL* ES drivers for your platform support. Table 1 provides a summary of the EGL* image surface types that are available for Android. Note that Android lists support for the EGL_KHR_image_pixmap extension, but it is actually the EGL_NATIVE_BUFFER_ANDROID surface type that you must use, notEGL_NATIVE_PIXMAP_KHR.

Table 1. Surface types for EGL* images on Android

Extension Surface type
EGL_NATIVE_PIXMAP_KHR Pixmap surface (not available on Android)
EGL_GL_TEXTURE_2D_KHR Conventional 2D texture
EGL_GL_TEXTURE_3D_KHR Conventional 3D texture
EGL_GL_RENDERBUFFER_KHR Render buffer surface for glReadPixels()
EGL_NATIVE_BUFFER_ANDROID For Android’s native graphics API

The code in Listing 5 shows how to use the EGL* image extension in two ways. First, on the Android platform, a native GraphicBuffer surface is created and locked. This buffer can be accessed for rendering while it is locked. When this buffer is unlocked, it can be imported into a new EGL* image with the ClientBufferAddress parameter to eglCreateImageKHR(). This EGL* image is then bound to GL_TEXTURE_2D with glEGLImageTargetTexture2DOES(), to be used as any texture can be used in OpenGL* ES. This is accomplished without ever copying the image, as the native GraphicBufferand the OpenGL* ES texture are actually sharing the same image data. This example demonstrates how images can be exchanged quickly between OpenGL* ES and Android or any 2D API on the Android platform. Note that the GraphicBuffer class is only available in the Android framework API, not the NDK.

If you are not using Android, you can still import images into OpenGL* ES textures in the same way. Set the ClientBufferAddress to point to your image data, and set the SurfaceType asEGL_GL_TEXTURE_2D_KHR. Refer to your eglext.h include file for a complete list of the surface types that are available on your platform. Use eglQuerySurface() to obtain the address, pitch (stride), and origin of the new EGL* image buffer after it is created. Be sure to use eglGetError() after each call to the EGL* to check for any returned errors.

Listing 5. Example of using the EGL* image extension with Android

#include <EGL/eglext.h>
#include <GLES2/gl2ext.h>
    
#ifdef    ANDROID
    GraphicBuffer * pGraphicBuffer = new GraphicBuffer(ImageWidth, ImageHeight, PIXEL_FORMAT_RGB_565, GraphicBuffer::USAGE_SW_WRITE_OFTEN | GraphicBuffer::USAGE_HW_TEXTURE);

// Lock the buffer to get a pointer
    unsigned char * pBitmap = NULL;
    pGraphicBuffer->lock(GraphicBuffer::USAGE_SW_WRITE_OFTEN,(void **)&pBitmap);

// Write 2D image to pBitmap

// Unlock to allow OpenGL ES to use it
    pGraphicBuffer->unlock();

EGLClientBuffer ClientBufferAddress = pGraphicBuffer->getNativeBuffer();
EGLint SurfaceType = EGL_NATIVE_BUFFER_ANDROID;
#else
EGLint SurfaceType = EGL_GL_TEXTURE_2D_KHR;
#endif

// Make an EGL Image at the same address of the native client buffer
EGLDisplay eglDisplayHandle = eglGetDisplay(EGL_DEFAULT_DISPLAY);

// Create an EGL Image with these attributes
EGLint eglImageAttributes[] = {EGL_WIDTH, ImageWidth, EGL_HEIGHT, ImageHeight, EGL_MATCH_FORMAT_KHR,  EGL_FORMAT_RGB_565_KHR, EGL_IMAGE_PRESERVED_KHR, EGL_TRUE, EGL_NONE};

EGLImageKHR eglImageHandle = eglCreateImageKHR(eglDisplayHandle, EGL_NO_CONTEXT, SurfaceType, ClientBufferAddress, eglImageAttributes);

// Create a texture and bind it to GL_TEXTURE_2D
EGLint TextureHandle;
glGenTextures(1, &TextureHandle);
glBindTexture(GL_TEXTURE_2D, TextureHandle);

// Attach the EGL Image to the same texture
glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, eglImageHandle);
    
// Get the address and pitch (stride) of the new texture image
eglQuerySurface(eglDisplayHandle, eglImageHandle, EGL_BITMAP_POINTER_KHR, &BitmapAddress);
eglQuerySurface(eglDisplayHandle, eglImageHandle, EGL_BITMAP_PITCH_KHR, &BitmapPitch);
eglQuerySurface(eglDisplayHandle, eglImageHandle, EGL_BITMAP_ORIGIN_KHR, &BitmapOrigin);
    
// Check for errors after each call to the EGL
if (eglGetError() != EGL_SUCCESS)
    break;
    
// Delete the EGL Image to free the memory when done
eglDestroyImageKHR(eglDisplayHandle, eglImageHandle);

Conclusion

One of the best ways to update an application with a tired 2D GUI is to exploit the accelerated OpenGL* ES features of Android on the Intel® Atom™ platform. Even though 2D and 3D are really different paradigms, the combination of the two is powerful. The trick is to make them cooperate by either sharing the frame buffer or sharing images through textures and the EGL* image extension. Use of this extension with OpenGL* ES is essential for achieving a good user experience, because the conventional method of loading textures with glTexImage2D() is too slow for dynamic images. Fortunately, this extension is well supported on most embedded platforms today, including Android.

https://software.intel.com/en-us/articles/using-opengl-es-to-accelerate-apps-with-legacy-2d-guis

EGLImage与纹理的更多相关文章

  1. OpenGL: 纹理采样 texture sample

    Sampler (GLSL) Sampler通常是在Fragment shader(片元着色器)内定义的,这是一个uniform类型的变量,即处理不同的片元时这个变量是一致不变的.一个sampler和 ...

  2. CSharpGL(10)两个纹理叠加

    CSharpGL(10)两个纹理叠加 本文很简单,只说明如何用shader实现叠加两个纹理的效果. 另外,最近CSharpGL对渲染框架做了修改,清理一些别扭的内容(DoRender()前后的事件都去 ...

  3. CSharpGL(8)使用3D纹理渲染体数据 (Volume Rendering) 初探

    CSharpGL(8)使用3D纹理渲染体数据 (Volume Rendering) 初探 2016-08-13 由于CSharpGL一直在更新,现在这个教程已经不适用最新的代码了.CSharpGL源码 ...

  4. D3D三层Texture纹理经像素着色器实现渲染YUV420P

    简单记录一下这两天用Texture实现渲染YUV420P的一些要点. 在视频播放的过程中,有的时候解码出来的数据是YUV420P的.表面(surface)通过设置参数是可以渲染YUV420P的,但Te ...

  5. 【转】OpenGL多线程创建纹理,附加我的测试结果

    原文地址 http://www.cnblogs.com/mazhenyu/archive/2010/04/29/1724190.html 关于这个问题以前只知道多个线程不能同时使用一个RC,结果为了能 ...

  6. Mipmap与纹理过滤

    为了加快渲染速度和减少纹理锯齿,贴图被处理成由一系列被预先计算和优化过的图片组成的文件,这样的贴图被称为Mipmap. 使用DirectX Texture Tool(DX自带工具)预生成Mipmap ...

  7. WebGL入门教程(五)-webgl纹理

    前面文章: WebGL入门教程(一)-初识webgl WebGL入门教程(二)-webgl绘制三角形 WebGL入门教程(三)-webgl动画 WebGL入门教程(四)-webgl颜色 这里就需要用到 ...

  8. [转]各种移动GPU压缩纹理的使用方法

    介绍了各种移动设备所使用的GPU,以及各个GPU所支持的压缩纹理的格式和使用方法.1. 移动GPU大全 目前移动市场的GPU主要有四大厂商系列:1)Imagination Technologies的P ...

  9. [Unity] Shader(着色器)之纹理贴图

    在Shader中,我们除了可以设定各种光线处理外,还可以增加纹理贴图. 使用 settexture 命令可以为着色器指定纹理. 示例代码: Shader "Sbin/ff2" { ...

随机推荐

  1. 集合映射Set(使用xml文件)

    如果持久类具有Set对象,可以在映射文件中使用set元素映射Set集合. set元素不需要索引元素. List和Set之间的区别是: Set只存储唯一的值. 我们来看看我们如何在映射文件中实现集合: ...

  2. MFC多国语言——配置文件

    前段时间,因工作需要,本地化了一个英文版本的产品. 在网上查阅了若干资料,在此进行一个简单的整理. 在MFC程序中,实现多国语言的方式很多,我们选择的是使用配置文件的方法. 在通过配置文件方式实现多国 ...

  3. Dmidecode

    一.Dmidecode简介 DMI (Desktop Management Interface, DMI)就是帮助收集电脑系统信息的管理系统,DMI信息的收集必须在严格遵照SMBIOS规范的前提下进行 ...

  4. iOS 设置Label中特定的文字大小和颜色

    直接上代码: _price = @"27"; NSMutableAttributedString *attributedString = [[NSMutableAttributed ...

  5. 使用bbed编辑研究oracle数据块结构

    bbed是随oracle软件公布的一款数据块查看和编辑工具,作为一款内部工具.bbed的功能很强大,可是假设使用不当可能给数据库造成无法挽回的损失.因此.我们建议在使用bbed改动数据块前备份被改动的 ...

  6. java8 关于日期的处理

    Java8 为我们提供了一种新的日期格式:LocalDate和LocalDateTime 获取当前的时间及前一天时间的方法: import java.time.LocalDateTime; impor ...

  7. C++STL容器(lower_bound,upper_bound)

    C++STL容器中有三种二分查找函数,这里分享其中的两个 这两个函数其实都可以理解为不破坏数组次序的前期下能将目标元素插入到数组的第几个位置,不过在细节上两个函数有所差异 int d[6]={0,2, ...

  8. oracelp---随意 记录(nvl)

    1.Oracle的Nvl函数 nvl( ) 函数 从两个表达式返回一个非null 值. 语法 NVL(eExpression1, eExpression2) 参数 eExpression1, eExp ...

  9. websocket集群情况下Nginx 代理出现的坑

    那么问题的背景: A想给B发送socket 消息 ! A这消息 这时候被Nginx 轮询发到了C 服务器上! 擦!   这时候就蛋疼了!   要接收消息那个人在B服务器上!     B就这样苦逼的收不 ...

  10. dev 小问题列表

    1. MemoEdit > Lines Text lines are separated by line feed and carriage return characters ("\ ...