If you are wanting a snapshot of what's on screen, this is what I'm doing in one of my camera apps. I haven't touched this code in a long time so there might be a better 5.0 way now but this is solid with over 1 million downloads. There is a function for grabbing a UIView based screen and one for grabbing an Open/GLES1 screen:
//
// ScreenCapture.m
// LiveEffectsCam
//
// Created by John Carter on 10/8/10.
//
#import "ScreenCapture.h"
#import <QuartzCore/CABase.h>
#import <QuartzCore/CATransform3D.h>
#import <QuartzCore/CALayer.h>
#import <QuartzCore/CAScrollLayer.h>
#import <OpenGLES/EAGL.h>
#import <OpenGLES/ES1/gl.h>
#import <OpenGLES/ES1/glext.h>
#import <QuartzCore/QuartzCore.h>
#import <OpenGLES/EAGLDrawable.h>
@implementation ScreenCapture
+ (UIImage *) GLViewToImage:(GLView *)glView
{
UIImage *glImage = [GLView snapshot:glView]; // returns an autoreleased image
return glImage;
}
+ (UIImage *) GLViewToImage:(GLView *)glView withOverlayImage:(UIImage *)overlayImage
{
UIImage *glImage = [GLView snapshot:glView]; // returns an autoreleased image
// Merge Image and Overlay
//
CGRect imageRect = CGRectMake((CGFloat)0.0, (CGFloat)0.0, glImage.size.width*glImage.scale, glImage.size.height*glImage.scale);
CGImageRef overlayCopy = CGImageCreateCopy( overlayImage.CGImage );
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, (int)glImage.size.width*glImage.scale, (int)glImage.size.height*glImage.scale, 8, (int)glImage.size.width*4*glImage.scale, colorSpace, kCGImageAlphaPremultipliedLast);
CGContextDrawImage(context, imageRect, glImage.CGImage);
CGContextDrawImage(context, imageRect, overlayCopy);
CGImageRef newImage = CGBitmapContextCreateImage(context);
UIImage *combinedViewImage = [[[UIImage alloc] initWithCGImage:newImage] autorelease];
CGImageRelease(newImage);
CGImageRelease(overlayCopy);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return combinedViewImage;
}
+ (UIImage *) UIViewToImage:(UIView *)view withOverlayImage:(UIImage *)overlayImage
{
UIImage *viewImage = [ScreenCapture UIViewToImage:view]; // returns an autoreleased image
// Merge Image and Overlay
//
CGRect imageRect = CGRectMake((CGFloat)0.0, (CGFloat)0.0, viewImage.size.width*viewImage.scale, viewImage.size.height*viewImage.scale);
CGImageRef overlayCopy = CGImageCreateCopy( overlayImage.CGImage );
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, (int)viewImage.size.width*viewImage.scale, (int)viewImage.size.height*viewImage.scale, 8, (int)viewImage.size.width*4*viewImage.scale, colorSpace, kCGImageAlphaPremultipliedLast);
CGContextDrawImage(context, imageRect, viewImage.CGImage);
CGContextDrawImage(context, imageRect, overlayCopy);
CGImageRef newImage = CGBitmapContextCreateImage(context);
UIImage *combinedViewImage = [[[UIImage alloc] initWithCGImage:newImage] autorelease];
CGImageRelease(newImage);
CGImageRelease(overlayCopy);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return combinedViewImage;
}
+ (UIImage *) UIViewToImage:(UIView *)view
{
// Create a graphics context with the target size
// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
//
// CGSize imageSize = [[UIScreen mainScreen] bounds].size;
CGSize imageSize = CGSizeMake( (CGFloat)480.0, (CGFloat)640.0 ); // camera image size
if (NULL != UIGraphicsBeginImageContextWithOptions)
UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);
else
UIGraphicsBeginImageContext(imageSize);
CGContextRef context = UIGraphicsGetCurrentContext();
// Start with the view...
//
CGContextSaveGState(context);
CGContextTranslateCTM(context, [view center].x, [view center].y);
CGContextConcatCTM(context, [view transform]);
CGContextTranslateCTM(context,-[view bounds].size.width * [[view layer] anchorPoint].x,-[view bounds].size.height * [[view layer] anchorPoint].y);
[[view layer] renderInContext:context];
CGContextRestoreGState(context);
// ...then repeat for every subview from back to front
//
for (UIView *subView in [view subviews])
{
if ( [subView respondsToSelector:@selector(screen)] )
if ( [(UIWindow *)subView screen] == [UIScreen mainScreen] )
continue;
CGContextSaveGState(context);
CGContextTranslateCTM(context, [subView center].x, [subView center].y);
CGContextConcatCTM(context, [subView transform]);
CGContextTranslateCTM(context,-[subView bounds].size.width * [[subView layer] anchorPoint].x,-[subView bounds].size.height * [[subView layer] anchorPoint].y);
[[subView layer] renderInContext:context];
CGContextRestoreGState(context);
}
UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); // autoreleased image
UIGraphicsEndImageContext();
return image;
}
+ (UIImage *) snapshot:(GLView *)eaglview
{
NSInteger x = 0;
NSInteger y = 0;
NSInteger width = [eaglview backingWidth];
NSInteger height = [eaglview backingHeight];
NSInteger dataLength = width * height * 4;
NSUInteger i;
for ( i=0; i<100; i++ )
{
glFlush();
CFRunLoopRunInMode(kCFRunLoopDefaultMode, (float)1.0/(float)60.0, FALSE);
}
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;
NSInteger 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(); // autoreleased image
UIGraphicsEndImageContext();
// Clean up
free(data);
CFRelease(ref);
CFRelease(colorspace);
CGImageRelease(iref);
return image;
}
@end
Best Answer
I have a very similar situation. I just have one view controller and I want to have a
AVCaptureVideoPreviewLayer
that doesn't rotate in it. I found the accepted solution by @SeanLintern88 did not work for me; the status bar never moved and the WKWebView I had on the screen was not getting resizes properly.One of the bigger issues I ran into was that I was putting my
AVCaptureVideoPreviewLayer
in the view controller's view. It is much better to create a newUIView
just to hold the layer.After that I found a technical note from Apple QA1890: Preventing a View From Rotating. This allowed me to produce the following swift code:
The original tech note did not have the line
self.previewView!.layer.frame = self.view.bounds
but I found that very necessary because although the anchor point doesn't move, the frame has. Without that line, the preview will be offset.Also, since I am doing all of the work keeping the view in the correct position, I had to remove all the positioning constraints on it. When I had them in, they would cause the preview to instead be offset in the opposite direction.