opengl es(iphone) render from file

问题

sorry for my english

I want to display video from a file, where the frames of 4 bytes per pixel, BRGA, 1280x720?

on mac I just took out the frame and drew this glDrawPixels, running on a Mac but in opengl es all differently.

here's the code from the mac

int pos = 0;
NSData *data = [[NSData alloc] initWithContentsOfFile:@"video.raw"];
glViewport(0,0,width,height);
glLoadIdentity();
glOrtho(0, width, 0, height, -1.0, 1.0);
glPixelZoom(1, -1);
glClear(GL_COLOR_BUFFER_BIT);
//glRasterPos2i(0, height);
glRasterPos2i(0, 0);
glDrawPixels(1280, 720, GL_BGRA, GL_UNSIGNED_BYTE, [data bytes]+pos);
glFinish();

回答1:

Push those data to texture with "glTexSubImage2D" and render the texture. Note though that texture has to be of power of 2 so for your case you can make it (2048, 1024) but you may update only the (1280, 720) part:

CGSize videoSize;
CGSize textureSize;
GLuint dimension = 1;
while (videoSize.width > dimension) {
    dimension <<= 1;
}
textureSize = CGSizeMake(dimension, .0f);
dimension = 1;
while (videoSize.height > dimension) {
    dimension <<= 1;
}
textureSize = CGSizeMake(textureSize.width, dimension);

GLuint texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
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, textureSize.width, textureSize.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);

GLfloat textureCoordinates[] = {
    .0f, .0f,
    .0f, videoSize.height/textureSize.height,
    videoSize.width/textureSize.width, .0f,
    videoSize.width/textureSize.width, videoSize.height/textureSize.height
};

To update the texture:

void *data;
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, videoSize.width, videoSize.height, GL_RGBA, GL_UNSIGNED_BYTE, data);

Then just draw your textured quad.

来源：https://stackoverflow.com/questions/13738110/opengl-esiphone-render-from-file

标签

ios

opengl-es

render