OpenGL ES View Snapshot

// IMPORTANT: Call this method after you draw and before -presentRenderbuffer:.
- (UIImage*)snapshot:(UIView*)eaglview
{
    GLint backingWidth, backingHeight;
 
    // Bind the color renderbuffer used to render the OpenGL ES view
    // If your application only creates a single color renderbuffer which is already bound at this point,
    // this call is redundant, but it is needed if you're dealing with multiple renderbuffers.
    // Note, replace "_colorRenderbuffer" with the actual name of the renderbuffer object defined in your class.
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, _colorRenderbuffer);
 
    // Get the size of the backing CAEAGLLayer
    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);
    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);
 
    NSInteger x = 0, y = 0, width = backingWidth, height = backingHeight;
    NSInteger dataLength = width * height * 4;
    GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte));
 
    // Read pixel data from the framebuffer
    glPixelStorei(GL_PACK_ALIGNMENT, 4);
    glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);
 
    // Create a CGImage with the pixel data
    // If your OpenGL ES content is opaque, use kCGImageAlphaNoneSkipLast to ignore the alpha channel
    // otherwise, use kCGImageAlphaPremultipliedLast
    CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL);
    CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
    CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast,
                                    ref, NULL, true, kCGRenderingIntentDefault);
 
    // OpenGL ES measures data in PIXELS
    // Create a graphics context with the target size measured in POINTS
    NSInteger widthInPoints, heightInPoints;
    if (NULL != UIGraphicsBeginImageContextWithOptions) {
        // On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
        // Set the scale parameter to your OpenGL ES view's contentScaleFactor
        // so that you get a high-resolution snapshot when its value is greater than 1.0
        CGFloat scale = eaglview.contentScaleFactor;
        widthInPoints = width / scale;
        heightInPoints = height / scale;
        UIGraphicsBeginImageContextWithOptions(CGSizeMake(widthInPoints, heightInPoints), NO, scale);
    }
    else {
        // On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
        widthInPoints = width;
        heightInPoints = height;
        UIGraphicsBeginImageContext(CGSizeMake(widthInPoints, heightInPoints));
    }
 
    CGContextRef cgcontext = UIGraphicsGetCurrentContext();
 
    // UIKit coordinate system is upside down to GL/Quartz coordinate system
    // Flip the CGImage by rendering it to the flipped bitmap context
    // The size of the destination area is measured in POINTS
    CGContextSetBlendMode(cgcontext, kCGBlendModeCopy);
    CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, widthInPoints, heightInPoints), iref);
 
    // Retrieve the UIImage from the current context
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
 
    UIGraphicsEndImageContext();
 
    // Clean up
    free(data);
    CFRelease(ref);
    CFRelease(colorspace);
    CGImageRelease(iref);
 
    return image;
}

 

2020/05/29 - [iOS/Objective-C] - Merge two different images in swift

2020/05/29 - [프로그래밍/C, C++] - Base64 encode / decode in C++

2020/05/29 - [OS/Mac OS X] - iPhone SDK location on hard drive

2020/05/29 - [iOS/Objective-C] - NSString <-> CBUUID 변환

2020/05/29 - [개발노트] - HTTP Content-Type

2020/05/28 - [iOS/Swift] - SEED 블록암호 알고리즘 CBC (Cipher Block Chaining) 예제

2020/05/28 - [개발노트] - HMAC SHA256

2020/05/26 - [iOS/Swift] - Array <-> Data 변환

2020/05/25 - [분류 전체보기] - UserAgent 추가

2020/05/25 - [iOS/Swift] - RSA 암호화 / 복호화

2020/05/25 - [iOS/Swift] - Base64 인코딩/디코딩

2020/05/19 - [AI/Algorithm] - Generic algorithm

2020/05/19 - [AI/Algorithm] - neural network

2020/05/19 - [AI/Algorithm] - minimax full search example

2020/05/19 - [AI/Algorithm] - minimax, alpha-beta pruning