To draw random picture with OpenGL ES in ios - ios

Question

I need to set random picture (type noise pixel) necessarily with using OpenGL ES. Without openGL (in ios) we have did it like this:
//declare variable:
UIImage* myImage;
UIImageView *imageView;
CGRect rect;
//function whitch drawing random pixel-array picture and display it on screen ios-device;
-(void)setPicture
{
if(imageView!=NULL)
{
//Addition removal imageView
[imageView removeFromSuperview];
imageView = NULL; //
}
int width = 352; //sizes
int height = 288;
size_t bufferLength = width * height * 4; //
uint8_t* pixels = (uint8_t*)malloc(bufferLength); //
for (int i = 0; i < bufferLength/2; i++) {
pixels[i] = rand() % 255; //obtain random pixel array
}
CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
CGContextRef ctx = CGBitmapContextCreate(pixels, width, height, 8, width * 4, space, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast); //
CGImageRef toCGImage = CGBitmapContextCreateImage(ctx);
UIImage * uiimage = [[UIImage alloc] initWithCGImage:toCGImage]; //reflect pixel array to picture
CGImageRelease(toCGImage);
CGColorSpaceRelease(space);
CGContextRelease(ctx);
free(pixels);
myImage = uiimage;
//
rect = self.view.bounds; //
if(imageView == NULL)
{
imageView = [[UIImageView alloc] initWithFrame:rect];
imageView.image = myImage;
[self.view addSubview:imageView];
NSLog(#"NULL");
} else
{
[imageView setNeedsDisplay];
NSLog(#"Dewnull");
}
}
Same picture displays on screen after calling of my function.
Questions
Is it possible to set similar picture on ios screen with openGL ES? How to make it? Will it work faster then my function?

Answer 1

See the section 'Procedural Textures: “Random” Noise'. Is it faster? to generate, almost certainly yes, because the GPU can easily parallelize this process. Reading back from the GPU can be slow though; I imagine maybe less so on iOS because the memory is unified. Profile it and see. It depends what you are doing with the texture.