Obtener una captura de pantalla de UIScrollView, incluidas las partes fuera de pantalla

Para mí respuesta https://stackoverflow.com/a/3539944/4164443 no funcionó. Tuve la tarea de implementar esto en iOS 8.

En realidad este método funciona para iPhone, pero iPad (tanto simu como dispositivo real) es otro caso. Solo hace parte visible y el resto de la imagen está en blanco.

Lo intenté con drawViewHierarchyInRect - no hubo suerte. Dependiendo de afterScreenUpdates ser true o false Me estiró parte de la imagen o de nuevo solo parte de la imagen.

Así que la única manera que encontré para lograr correcta screenshoting es agregar scrollview a otra vista temporal y renderizarla.

El código de ejemplo está debajo (scrollview es outlet en mi VC)

func getImageOfScrollView()->UIImage{
    var image = UIImage();

    UIGraphicsBeginImageContextWithOptions(self.scrollView.contentSize, false, UIScreen.mainScreen().scale)

    // save initial values
    let savedContentOffset = self.scrollView.contentOffset;
    let savedFrame = self.scrollView.frame;
    let savedBackgroundColor = self.scrollView.backgroundColor

    // reset offset to top left point
    self.scrollView.contentOffset = CGPointZero;
    // set frame to content size
    self.scrollView.frame = CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height);
    // remove background
    self.scrollView.backgroundColor = UIColor.clearColor()

    // make temp view with scroll view content size
    // a workaround for issue when image on ipad was drawn incorrectly
    let tempView = UIView(frame: CGRectMake(0, 0, self.scrollView.contentSize.width, self.scrollView.contentSize.height))

    // save superview
    let tempSuperView = self.scrollView.superview
    // remove scrollView from old superview
    self.scrollView.removeFromSuperview()
    // and add to tempView
    tempView.addSubview(self.scrollView)

    // render view
    // drawViewHierarchyInRect not working correctly
    tempView.layer.renderInContext(UIGraphicsGetCurrentContext())
    // and get image
    image = UIGraphicsGetImageFromCurrentImageContext();

    // and return everything back
    tempView.subviews[0].removeFromSuperview()
    tempSuperView?.addSubview(self.scrollView)

    // restore saved settings
    self.scrollView.contentOffset = savedContentOffset;
    self.scrollView.frame = savedFrame;
    self.scrollView.backgroundColor = savedBackgroundColor

    UIGraphicsEndImageContext();

    return image
}

Ejemplo de trabajo de la extensión UIView con manejo para UIScrollView:

extension UIView {
    func screenshot() -> UIImage {

            if(self is UIScrollView) {
                let scrollView = self as! UIScrollView

                let savedContentOffset = scrollView.contentOffset
                let savedFrame = scrollView.frame

                UIGraphicsBeginImageContext(scrollView.contentSize)
                scrollView.contentOffset = .zero
                self.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)
                self.layer.render(in: UIGraphicsGetCurrentContext()!)
                let image = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext();

                scrollView.contentOffset = savedContentOffset
                scrollView.frame = savedFrame

                return image!
            }

            UIGraphicsBeginImageContext(self.bounds.size)
            self.layer.render(in: UIGraphicsGetCurrentContext()!)
            let image = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            return image!

        }
}

Tomé la solución anterior de @Roopesh Mittal y la hice más segura/limpia.

Compatible con Swift 4

fileprivate extension UIScrollView {
    func screenshot() -> UIImage? {
        let savedContentOffset = contentOffset
        let savedFrame = frame

        UIGraphicsBeginImageContext(contentSize)
        contentOffset = .zero
        frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)

        guard let context = UIGraphicsGetCurrentContext() else { return nil }

        layer.render(in: context)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext();

        contentOffset = savedContentOffset
        frame = savedFrame

        return image
    }
}

Si no desea expandir su vista de desplazamiento más allá de toda la pantalla (y no funcionará con el diseño automático de todos modos) hay una mejor manera.

Puede usar transformaciones de gráficos centrales junto con contentOffset de la vista de desplazamiento para lograr lo mismo.

//
//  ScrollViewSnapshotter.swift
//  ScrollViewSnapshotter
//
//  Created by Moshe Berman on 4/10/16.
//  Copyright © 2016 Moshe Berman. All rights reserved.
//

import UIKit

class ScrollViewSnapshotter: NSObject {


func PDFWithScrollView(scrollview: UIScrollView) -> NSData {

    /**
     *  Step 1: The first thing we need is the default origin and size of our pages.
     *          Since bounds always start at (0, 0) and the scroll view's bounds give us
     *          the correct size for the visible area, we can just use that.
     *
     *          In the United States, a standard printed page is 8.5 inches by 11 inches,
     *          but when generating a PDF it's simpler to keep the page size matching the
     *          visible area of the scroll view. We can let our printer software (such
     *          as the Preview app on OS X or the Printer app on iOS) do the scaling.
     *
     *          If we wanted to scale ourselves, we could multiply each of those
     *          numbers by 72, to get the number of points for each dimension.
     *          We would have to change how we generated the the pages below, so
     *          for simplicity, we're going to stick to one page per screenful of content.
     */

    let pageDimensions = scrollview.bounds

    /**
     *  Step 2: Now we need to know how many pages we will need to fit our content.
     *          To get this, we divide our scroll views dimensions by the size
     *          of each page, in either direction.
     *          We also need to round up, so that the pages don't get clipped.
     */

    let pageSize = pageDimensions.size
    let totalSize = scrollview.contentSize

    let numberOfPagesThatFitHorizontally = Int(ceil(totalSize.width / pageSize.width))
    let numberOfPagesThatFitVertically = Int(ceil(totalSize.height / pageSize.height))

    /**
     *  Step 3: Set up a Core Graphics PDF context.
     *
     *          First we create a backing store for the PDF data, then
     *          pass it and the page dimensions to Core Graphics.
     *
     *          We could pass in some document information here, which mostly cover PDF metadata,
     *          including author name, creator name (our software) and a password to
     *          require when viewing the PDF file.
     *
     *          Also note that we can use UIGraphicsBeginPDFContextToFile() instead,
     *          which writes the PDF to a specified path. I haven't played with it, so
     *          I don't know if the data is written all at once, or as each page is closed.
     */

    let outputData = NSMutableData()

    UIGraphicsBeginPDFContextToData(outputData, pageDimensions, nil)

    /**
     *  Step 4: Remember some state for later.
     *          Then we need to clear the content insets, so that our
     *          core graphics layer and our content offset match up.
     *          We don't need to reset the content offset, because that
     *          happens implicitly, in the loop below.
     */

    let savedContentOffset = scrollview.contentOffset
    let savedContentInset = scrollview.contentInset

    scrollview.contentInset = UIEdgeInsetsZero

    /**
     *  Step 6: Now we loop through the pages and generate the data for each page.
     */

    if let context = UIGraphicsGetCurrentContext()
    {
        for indexHorizontal in 0 ..< numberOfPagesThatFitHorizontally
        {
            for indexVertical in 0 ..< numberOfPagesThatFitVertically
            {

                /**
                 *  Step 6a: Start a new page.
                 *
                 *          This automatically closes the previous page.
                 *          There's a similar method UIGraphicsBeginPDFPageWithInfo,
                 *          which allows you to configure the rectangle of the page and
                 *          other metadata.
                 */

                UIGraphicsBeginPDFPage()

                /**
                 *  Step 6b:The trick here is to move the visible portion of the
                 *          scroll view *and* adjust the core graphics context
                 *          appropriately.
                 *
                 *          Consider that the viewport of the core graphics context
                 *          is attached to the top of the scroll view's content view
                 *          and we need to push it in the opposite direction as we scroll.
                 *          Further, anything not inside of the visible area of the scroll
                 *          view is clipped, so scrolling will move the core graphics viewport
                 *          out of the rendered area, producing empty pages.
                 *
                 *          To counter this, we scroll the next screenful into view, and adjust
                 *          the core graphics context. Note that core graphics uses a coordinate
                 *          system which has the y coordinate decreasing as we go from top to bottom.
                 *          This is the opposite of UIKit (although it matches AppKit on OS X.)
                 */

                let offsetHorizontal = CGFloat(indexHorizontal) * pageSize.width
                let offsetVertical = CGFloat(indexVertical) * pageSize.height

                scrollview.contentOffset = CGPointMake(offsetHorizontal, offsetVertical)
                CGContextTranslateCTM(context, -offsetHorizontal, -offsetVertical) // NOTE: Negative offsets

                /**
                 *  Step 6c: Now we are ready to render the page.
                 *
                 *  There are faster ways to snapshot a view, but this
                 *  is the most straightforward way to render a layer
                 *  into a context.
                 */

                scrollview.layer.renderInContext(context)
            }
        }
    }

    /**
     *  Step 7: End the document context.
     */

    UIGraphicsEndPDFContext()

    /**
     *  Step 8: Restore the scroll view.
     */

    scrollview.contentInset = savedContentInset
    scrollview.contentOffset = savedContentOffset

    /**
     *  Step 9: Return the data.
     *          You can write it to a file, or display it the user,
     *          or even pass it to iOS for sharing.
     */

    return outputData
}
}

Aquí hay una entrada de blog que escribí explicando el proceso.

El proceso para generar un PDF es muy similar al snapshotting de una imagen, excepto que en lugar de páginas, tendría que hacer un lienzo grande que coincide con el tamaño de la vista de desplazamiento y luego agarrar el contenido en trozos.

Versión SWIFT 3:

func snapshot() -> UIImage?
{      
    UIGraphicsBeginImageContext(scrollView.contentSize)

    let savedContentOffset = scrollView.contentOffset
    let savedFrame = scrollView.frame

    scrollView.contentOffset = CGPoint.zero
    scrollView.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)

    scrollView.layer.render(in: UIGraphicsGetCurrentContext()!)
    let image = UIGraphicsGetImageFromCurrentImageContext()

    scrollView.contentOffset = savedContentOffset
    scrollView.frame = savedFrame

    UIGraphicsEndImageContext()

    return image
}

Esto funcionó para mí

Una versión refinada de Swift 4.1, basada en la respuesta de @RyanG:

fileprivate extension UIScrollView {
    func screenshot() -> UIImage? {
        // begin image context
        UIGraphicsBeginImageContextWithOptions(contentSize, false, 0.0)
        // save the orginal offset & frame 
        let savedContentOffset = contentOffset
        let savedFrame = frame
        // end ctx, restore offset & frame before returning
        defer {
            UIGraphicsEndImageContext()
            contentOffset = savedContentOffset
            frame = savedFrame
        }
        // change the offset & frame so as to include all content
        contentOffset = .zero
        frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
        guard let ctx = UIGraphicsGetCurrentContext() else {
            return nil
        }
        layer.render(in: ctx)
        let image = UIGraphicsGetImageFromCurrentImageContext()

        return image
    }
}

No se mucho pero puedo adivinar que si establecemos el tamaño del contextRect como este para el paisaje, puede funcionar bien:

  CGRect contextRect  = CGRectMake(0, 0, 1004, 768*2);

Debido a que este contextRect determinará el tamaño de la UIGraphicsBeginImageContext así que espero que el doble de la altura puede resolver su problema

Aquí hay otra forma de hacerlo, que tiene en cuenta el nivel de zoom. Tengo un scrollview con 4 capas UIImageView diferentes en él, y quiero tomar una captura de pantalla de su estado actual:

float theScale = 1.0f / theScrollView.zoomScale;
// The viewing rectangle in absolute coordinates
CGRect visibleArea = CGRectMake((int)(theScrollView.contentOffset.x * theScale), (int)(theScrollView.contentOffset.y * theScale),
                                (int)(theScrollView.bounds.size.width * theScale), (int)(theScrollView.bounds.size.height * theScale));

NSArray *layers = [NSArray arrayWithObjects:imageLayer1, imageLayer2, imageLayer3, imageLayer4, nil];
UIGraphicsBeginImageContext(visibleArea.size);
for (UIImageView *layer in layers) {
    CALayer *coreLayer = layer.layer;
    coreLayer.bounds = CGRectMake(layer.frame.origin.x - visibleArea.origin.x, layer.frame.origin.y - visibleArea.origin.y, layer.frame.size.width, layer.frame.size.height);
    [coreLayer renderInContext:UIGraphicsGetCurrentContext()];
}
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Esto toma la captura de pantalla en coordenadas absolutas. Es decir, si tiene una imagen 2048 * 2048 en el scrollview y puede ver aproximadamente una cuarta parte de ella, independientemente de la resolución de su pantalla, tomaría una captura de pantalla de 512*512. Si desea tomar una captura de pantalla en su resolución de pantalla (por ejemplo, 320 * 480) entonces usted tiene que ajustar la imagen de la siguiente manera, directamente después del código anterior:

UIGraphicsBeginImageContext(theScrollView.frame.size);
[screenshot drawInRect:CGRectMake(0, 0, theScrollView.frame.size.width, theScrollView.frame.size.height)];
UIImage *smallScreenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Versión SWIFT 3 gracias a @ gleb vodovozov:

func getImageOfScrollView()->UIImage{
    var image = UIImage();

    UIGraphicsBeginImageContextWithOptions(self.scrollView.contentSize, false, UIScreen.main.scale)

    // save initial values
    let savedContentOffset = self.scrollView.contentOffset;
    let savedFrame = self.scrollView.frame;
    let savedBackgroundColor = self.scrollView.backgroundColor

    // reset offset to top left point
    self.scrollView.contentOffset = CGPoint.zero;
    // set frame to content size
    self.scrollView.frame = CGRect(x: 0, y: 0, width: self.scrollView.contentSize.width, height: self.scrollView.contentSize.height)
    // remove background
    self.scrollView.backgroundColor = UIColor.clear

    // make temp view with scroll view content size
    // a workaround for issue when image on ipad was drawn incorrectly
    let tempView = UIView(frame: CGRect(x: 0, y: 0, width: self.scrollView.contentSize.width, height: self.scrollView.contentSize.height))

    // save superview
    let tempSuperView = self.scrollView.superview
    // remove scrollView from old superview
    self.scrollView.removeFromSuperview()
    // and add to tempView
    tempView.addSubview(self.scrollView)

    // render view
    // drawViewHierarchyInRect not working correctly
    tempView.layer.render(in: UIGraphicsGetCurrentContext()!)
    // and get image
    image = UIGraphicsGetImageFromCurrentImageContext()!;

    // and return everything back
    tempView.subviews[0].removeFromSuperview()
    tempSuperView?.addSubview(self.scrollView)

    // restore saved settings
    self.scrollView.contentOffset = savedContentOffset;
    self.scrollView.frame = savedFrame;
    self.scrollView.backgroundColor = savedBackgroundColor

    UIGraphicsEndImageContext();

    return image
}