Taking a screnshot of a UIView iOS - ios

Question

I want to take a screenshot of a UIView (the view would contain a signature) and save it to a local file in the application files, so that the image can be called up at a later point to be displayed in something like a UIImageView. Below is the code behind the signature UIView.
#import "NISignatureViewQuartz.h"
#import <QuartzCore/QuartzCore.h>
#implementation NISignatureViewQuartz
UIBezierPath *path;
- (void)commonInit
{
path = [UIBezierPath bezierPath];
// Capture touches
UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(pan:)];
pan.maximumNumberOfTouches = pan.minimumNumberOfTouches = 1;
[self addGestureRecognizer:pan];
// Erase with long press
[self addGestureRecognizer:[[UILongPressGestureRecognizer alloc] initWithTarget:self action:#selector(erase)]];
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
if (self = [super initWithCoder:aDecoder]) [self commonInit];
return self;
}
- (id)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) [self commonInit];
return self;
}
- (void)erase
{
path = [UIBezierPath bezierPath];
[self setNeedsDisplay];
}
- (void)pan:(UIPanGestureRecognizer *)pan {
CGPoint currentPoint = [pan locationInView:self];
if (pan.state == UIGestureRecognizerStateBegan) {
[path moveToPoint:currentPoint];
} else if (pan.state == UIGestureRecognizerStateChanged)
[path addLineToPoint:currentPoint];
[self setNeedsDisplay];
}
- (void)drawRect:(CGRect)rect
{
[[UIColor blackColor] setStroke];
[path stroke];
}
#end
How would I go about doing this?

Answer 1

You want to render the view's layer into a graphics context. It's very straightforward. In your NISignatureViewQuartz class you can add this method:
- (UIImage *)snapshot {
UIGraphicsBeginImageContext(self.frame.size);
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}

Answer 2

I wrote an useful helper class, to take and manage screenshot:
#implementation MGImageHelper
/* Get the screenshot of an UIView (so take just UIKit elements and not OpenGL or AVFoundation stuff. */
+ (UIImage *)getScreenshotFromView:(UIView *)captureView
{
CGRect rect = [captureView bounds];
UIGraphicsBeginImageContextWithOptions(rect.size,YES,0.0f);
CGContextRef context = UIGraphicsGetCurrentContext();
[captureView.layer renderInContext:context];
UIImage *capturedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return capturedImage;
}
/* Get the screenshot of a determinate rect of an UIView, and scale it to the size that you want. */
+ (UIImage *)getScreenshotFromView:(UIView *)captureView withRect:(CGRect)captureRect andScaleToSize:(CGSize)newSize
{
UIImage *image = [[self class] getScreenshotFromView:captureView];
image = [[self class] cropImage:image withRect:captureRect];
image = [[self class] scaleImage:image toSize:newSize];
return image;
}
/* Get the screenshot of the screen (useful when you have UIKit elements and OpenGL or AVFoundation stuff */
+ (UIImage *)screenshotFromScreen
{
CGImageRef UIGetScreenImage(void);
CGImageRef screen = UIGetScreenImage();
UIImage* screenImage = [UIImage imageWithCGImage:screen];
CGImageRelease(screen);
return screenImage;
}
/* Get the screenshot of a determinate rect of the screen, and scale it to the size that you want. */
+ (UIImage *)getScreenshotFromScreenWithRect:(CGRect)captureRect andScaleToSize:(CGSize)newSize
{
UIImage *image = [[self class] screenshotFromScreen];
image = [[self class] cropImage:image withRect:captureRect];
image = [[self class] scaleImage:image toSize:newSize];
return image;
}
/* Methods used from methods above but also usable in singular */
+ (UIImage *)cropImage:(UIImage *)image withRect:(CGRect)rect
{
CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect);
UIImage *cropedImage = [UIImage imageWithCGImage:imageRef];
return cropedImage;
}
+ (UIImage *)scaleImage:(UIImage *)image toSize:(CGSize)newSize
{
UIGraphicsBeginImageContextWithOptions(newSize, YES, 0.0);
[image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}
#end

Answer 3

You can use UIView method available starting from iOS 7, designed specifically for that:
- (BOOL)drawViewHierarchyInRect:(CGRect)rect afterScreenUpdates:(BOOL)afterUpdates;
e.g.
UIGraphicsBeginImageContext(self.bounds.size);
[self drawViewHierarchyInRect:self.bounds afterScreenUpdates:NO];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();