如何在GLES2中显示图像纹理。
在以下源初始化GLES2显示，表面..， 创建离线帧缓冲区， 将RGBA图像加载到纹理
以蓝色清除屏幕， 试图显示加载的图像纹理（..无法为GLES2找到正确的API） 阅读FBO＆amp;写入文件。
用于显示glEnableClientState＆amp; glVertexPointer API在GLES2中不支持 如何在GLES2中显示加载的图像纹理。 在下面的源中，从glReadPixels
获取缓冲区中只有蓝色unsigned char *video_raw = loadFile("./video.raw");//RGBA raw image
int iConfigs;
EGLConfig eglConfig;
EGLint ai32ContextAttribs[] = { EGL_CONTEXT_CLIENT_VERSION, 2,EGL_NONE };
EGLDisplay eglDisplay = eglGetDisplay((EGLNativeDisplayType)0);
eglInitialize(eglDisplay, 0, 0);
eglBindAPI(EGL_OPENGL_ES_API);
EGLint pi32ConfigAttribs[5];
pi32ConfigAttribs[0] = EGL_SURFACE_TYPE;
pi32ConfigAttribs[1] = EGL_WINDOW_BIT;
pi32ConfigAttribs[2] = EGL_RENDERABLE_TYPE;
pi32ConfigAttribs[3] = EGL_OPENGL_ES2_BIT;
pi32ConfigAttribs[4] = EGL_NONE;
eglChooseConfig(eglDisplay, pi32ConfigAttribs, &eglConfig, 1, &iConfigs);
EGLSurface eglSurface = eglCreatePbufferSurface(eglDisplay, eglConfig, NULL);
EGLContext eglContext = eglCreateContext(eglDisplay, eglConfig, NULL, ai32ContextAttribs);
eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext);
GLuint fboId = 0;
GLuint renderBufferWidth = 960;
GLuint renderBufferHeight = 540;
glGenFramebuffers(1, &fboId);
glBindFramebuffer(GL_FRAMEBUFFER, fboId);
GLuint renderBuffer;
glGenRenderbuffers(1, &renderBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGB565, renderBufferWidth, renderBufferHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderBuffer);
glClearColor(0.0,0.0,1.0,1.0);
glClear(GL_COLOR_BUFFER_BIT);
glEnable(GL_TEXTURE_2D);
GLuint texture_object_id;
glGenTextures(1, &texture_object_id);
glBindTexture(GL_TEXTURE_2D, texture_object_id);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, renderBufferWidth, renderBufferHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, video_raw);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
GLfloat vtx1[] = { -1, -1, 0, -1, 1, 0, 1, 1, 0, 1, -1, 0 };
GLfloat tex1[] = { 0, 0, 0, 1, 1, 1, 1, 0 };
/*glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, vtx1);
glTexCoordPointer(2, GL_FLOAT, 0, tex1);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);*/
eglSwapBuffers( eglDisplay, eglSurface);
//read & write to a file
int size = 4 * renderBufferHeight * renderBufferWidth;
unsigned char *data2 = new unsigned char[size];
glReadPixels(0, 0, renderBufferWidth, renderBufferHeight, GL_RGBA, GL_UNSIGNED_BYTE, data2);
dumptoFile("./read1.raw", size, data2);
修改1：
@ Rabbid76， 谢谢回复。当我使用你的vertx着色器“in vec3 inPos; \ n”着色器编译失败。我将“in”替换为“uniform”。
在添加输入的情况下从以下来源获取黑屏。
static const GLuint WIDTH = 960;
static const GLuint HEIGHT = 540;
static const GLchar* vertex_shader_source =
"#version 100\n"
"precision mediump float;\n"
"uniform vec3 inPos;\n"
"uniform vec2 inUV;\n"
"varying vec2 vUV;\n"
"void main(){\n"
" vUV = inUV;\n"
" gl_Position = vec4(inPos, 1.0);\n"
"}\n";
static const GLchar* fragment_shader_source =
"#version 100\n"
"precision mediump float;\n"
"varying vec2 vUV;\n"
"uniform sampler2D u_texture;\n"
"void main(){\n"
" gl_FragColor = texture2D(u_texture, vUV);\n"
"}\n";
int main(int argc, char **argv)
{
unsigned char *video_raw = loadFile("./video.raw");
int iConfigs;
EGLConfig eglConfig;
EGLint ai32ContextAttribs[] = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
EGLDisplay eglDisplay = eglGetDisplay((EGLNativeDisplayType) 0);
eglInitialize(eglDisplay, 0, 0);
eglBindAPI(EGL_OPENGL_ES_API);
EGLint pi32ConfigAttribs[5];
pi32ConfigAttribs[0] = EGL_SURFACE_TYPE;
pi32ConfigAttribs[1] = EGL_WINDOW_BIT;
pi32ConfigAttribs[2] = EGL_RENDERABLE_TYPE;
pi32ConfigAttribs[3] = EGL_OPENGL_ES2_BIT;
pi32ConfigAttribs[4] = EGL_NONE;
eglChooseConfig(eglDisplay, pi32ConfigAttribs, &eglConfig, 1, &iConfigs);
EGLSurface eglSurface = eglCreatePbufferSurface(eglDisplay, eglConfig, NULL);
EGLContext eglContext = eglCreateContext(eglDisplay, eglConfig, NULL, ai32ContextAttribs);
eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext);
GLuint shader_program, framebuffer, renderBuffer;
glGenRenderbuffers(1, &renderBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA, WIDTH, HEIGHT);
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderBuffer);
glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glViewport(0, 0, WIDTH, HEIGHT);
glEnable(GL_TEXTURE_2D);
shader_program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
GLint vert_inx = glGetAttribLocation(shader_program, "inPos");
GLint uv_inx = glGetAttribLocation(shader_program, "inUV");
GLint tex_loc = glGetUniformLocation(shader_program, "u_texture");
GLuint texture_object_id;
glGenTextures(1, &texture_object_id);
glBindTexture(GL_TEXTURE_2D, texture_object_id);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, WIDTH, HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, video_raw);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
GLfloat vtx1[] = { -1, -1, 0, -1, 1, 0, 1, 1, 0, 1, -1, 0 };
GLfloat tex1[] = { 0, 0, 0, 1, 1, 1, 1, 0 };
glVertexAttribPointer(vert_inx, 3, GL_FLOAT, GL_FALSE, 0, vtx1);
glEnableVertexAttribArray(vert_inx);
glVertexAttribPointer(uv_inx, 2, GL_FLOAT, GL_FALSE, 0, tex1);
glEnableVertexAttribArray(uv_inx);
glViewport(0,0,renderBufferWidth,renderBufferHeight);
glUseProgram(shader_program);
glUniform1i(tex_loc, 0);
glDrawArrays( GL_TRIANGLE_FAN, 0, 4);
glFlush();
int size = 4 * WIDTH * HEIGHT;
unsigned char *data2 = new unsigned char[size];
glReadPixels(0, 0, WIDTH, HEIGHT, GL_RGBA, GL_UNSIGNED_BYTE, data2);
dumptoFile("./read1.raw", size, data2);
return EXIT_SUCCESS;
}
答案 0 :(得分：1)
您必须使用着色器程序，并定义通用顶点属性数据的数组。另请参阅Vertex Specification。
创建，编译和链接一个非常简单的着色器程序，如下所示：
@Override
public void onStop() {
super.onStop();
if (mAdapter != null) {
mAdapter.stopListening();
}
}
const char *sh_vert =
"#version 100\n"\
"precision mediump float;\n"\
"attribute vec3 inPos;\n"\
"attribute vec2 inUV;\n"\
"varying vec2 vUV;\n"\
"void main()\n"\
"{\n"\
" vUV = inUV;\n"\
" gl_Position = vec4(inPos, 1.0);\n"\
"}";
const char *sh_frag =
"#version 100\n"\
"precision mediump float;\n"\
"varying vec2 vUV;\n"\
"uniform sampler2D u_texture;\n"\
"void main()\n"\
"{\n"\
" gl_FragColor = texture2D(u_texture, vUV);\n"\
"}";
获取属性索引和纹理采样器的位置均匀：
GLuint v_sh = glCreateShader( GL_VERTEX_SHADER );
glShaderSource( v_sh, 1, &sh_vert, nullptr );
glCompileShader( v_sh );
GLint status = GL_TRUE;
glGetShaderiv( v_sh, GL_COMPILE_STATUS, &status );
if ( status == GL_FALSE )
{
// compile error
}
GLuint f_sh = glCreateShader( GL_FRAGMENT_SHADER );
glShaderSource( f_sh, 1, &sh_frag, nullptr );
glCompileShader( f_sh );
status = GL_TRUE;
glGetShaderiv( f_sh, GL_COMPILE_STATUS, &status );
if ( status == GL_FALSE )
{
// compile error
}
GLuint prog = glCreateProgram();
glAttachShader( prog, v_sh );
glAttachShader( prog, f_sh );
glLinkProgram( prog );
status = GL_TRUE;
glGetProgramiv( prog, GL_LINK_STATUS, &status );
if ( status == GL_FALSE )
{
// link error
}
然后按（glVertexAttribPointer）定义通用顶点属性数据的数组，并按glEnableVertexAttribArray启用它们：
GLint vert_inx = glGetAttribLocation( prog, "inPos" );
GLint uv_inx = glGetAttribLocation( prog, "inUV" );
GLint tex_loc = glGetUniformLocation( prog, "u_texture" );
设置渲染缓冲区和帧缓冲区并调整视口：
GLfloat vtx1[] = { -1, -1, 0, -1, 1, 0, 1, 1, 0, 1, -1, 0 };
GLfloat tex1[] = { 0, 0, 0, 1, 1, 1, 1, 0 };
glVertexAttribPointer( vert_inx, 3, GL_FLOAT, GL_FALSE, 0, vtx1);
glEnableVertexAttribArray( vert_inx );
glVertexAttribPointer( uv_inx, 2, GL_FLOAT, GL_FALSE, 0, tex1);
glEnableVertexAttribArray( uv_inx );
使用该程序，将纹理采样器设置为均匀并绘制几何图形：
glGenFramebuffers(1, &fboId);
glBindFramebuffer(GL_FRAMEBUFFER, fboId);
GLuint renderBuffer;
glGenRenderbuffers(1, &renderBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA, renderBufferWidth, renderBufferHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderBuffer);
glViewport(0,0,renderBufferWidth,renderBufferHeight);
glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
最后可以读取图像：
// use the program
glUseProgram( prog );
glUniform1i( tex_loc, 0 ); // 0 == texture unit 0
// draw the geometry
glDrawArrays( GL_TRIANGLE_FAN, 0, 4 );
glUseProgram( 0 );