MyViewController.m
/* |
Copyright (C) 2015 Apple Inc. All Rights Reserved. |
See LICENSE.txt for this sample’s licensing information |
Abstract: |
Main view controller for displaying the image, reflection and slider table. |
*/ |
#import "MyViewController.h" |
#import "SliderCell.h" |
@interface MyViewController () <UITableViewDelegate, UITableViewDataSource> |
@property (nonatomic, strong) IBOutlet UIImageView *imageView; |
@property (nonatomic, strong) IBOutlet UIImageView *reflectionView; |
@property (nonatomic, strong) IBOutlet UITableView *slidersTableView; |
@property (nonatomic, strong) IBOutlet NSLayoutConstraint *reflectionViewHeightConstraint; |
@end |
#pragma mark - |
@implementation MyViewController |
// image reflection |
static const CGFloat kDefaultReflectionFraction = 0.65; |
static const CGFloat kDefaultReflectionOpacity = 0.40; |
static NSString *kCellID = @"CellID"; |
- (void)viewDidLoad |
{ |
[super viewDidLoad]; |
self.imageView.image = [UIImage imageNamed:@"scene.jpg"]; |
[self.slidersTableView registerClass:[SliderCell class] forCellReuseIdentifier:kCellID]; |
self.slidersTableView.backgroundColor = [UIColor whiteColor]; |
self.view.autoresizesSubviews = YES; |
self.view.userInteractionEnabled = YES; |
// determine the size of the reflection to create |
int reflectionHeight = self.imageView.bounds.size.height * kDefaultReflectionFraction; |
// create the reflection image and assign it to the UIImageView |
self.reflectionView.image = [self reflectedImage:self.imageView withHeight:reflectionHeight]; |
self.reflectionView.alpha = kDefaultReflectionOpacity; |
} |
#pragma mark - slider action methods |
- (IBAction)sizeSlideAction:(id)sender |
{ |
UISlider *slider = (UISlider *)sender; |
CGFloat val = [slider value]; |
// change the height constraint of our reflected image view |
NSInteger reflectionHeight = 180 * val; // 180 is the original maximum height of the reflected image |
self.reflectionViewHeightConstraint.constant = reflectionHeight; |
// create the reflection image, assign it to the UIImageView and add the image view to the containerView |
self.reflectionView.image = [self reflectedImage:self.imageView withHeight:reflectionHeight]; |
// get the alpha slider value, keep it set on the reflection |
UISlider *alphaSlider = (UISlider *)[[self.slidersTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:1 inSection:0]].contentView viewWithTag:kSliderTag]; |
self.reflectionView.alpha = alphaSlider.value; |
UITableViewCell *sliderCell = [self.slidersTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]]; |
sliderCell.detailTextLabel.text = [NSString stringWithFormat:@"%0.2f", val]; |
} |
- (IBAction)alphaSlideAction:(id)sender |
{ |
UISlider *slider = (UISlider *)sender; |
CGFloat val = [slider value]; |
self.reflectionView.alpha = val; |
[self.slidersTableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:1 inSection:0]].detailTextLabel.text = [NSString stringWithFormat:@"%0.2f", val]; |
} |
#pragma mark - Image Reflection |
CGImageRef CreateGradientImage(NSInteger pixelsWide, NSInteger pixelsHigh) |
{ |
CGImageRef theCGImage = NULL; |
// gradient is always black-white and the mask must be in the gray colorspace |
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); |
// create the bitmap context |
CGContextRef gradientBitmapContext = CGBitmapContextCreate(NULL, pixelsWide, pixelsHigh, |
8, 0, colorSpace, kCGImageAlphaNone); |
// define the start and end grayscale values (with the alpha, even though |
// our bitmap context doesn't support alpha the gradient requires it) |
CGFloat colors[] = {0.0, 1.0, 1.0, 1.0}; |
// create the CGGradient and then release the gray color space |
CGGradientRef grayScaleGradient = CGGradientCreateWithColorComponents(colorSpace, colors, NULL, 2); |
CGColorSpaceRelease(colorSpace); |
// create the start and end points for the gradient vector (straight down) |
CGPoint gradientStartPoint = CGPointZero; |
CGPoint gradientEndPoint = CGPointMake(0, pixelsHigh); |
// draw the gradient into the gray bitmap context |
CGContextDrawLinearGradient(gradientBitmapContext, grayScaleGradient, gradientStartPoint, |
gradientEndPoint, kCGGradientDrawsAfterEndLocation); |
CGGradientRelease(grayScaleGradient); |
// convert the context into a CGImageRef and release the context |
theCGImage = CGBitmapContextCreateImage(gradientBitmapContext); |
CGContextRelease(gradientBitmapContext); |
// return the imageref containing the gradient |
return theCGImage; |
} |
CGContextRef MyCreateBitmapContext(NSInteger pixelsWide, NSInteger pixelsHigh) |
{ |
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); |
// create the bitmap context |
CGContextRef bitmapContext = CGBitmapContextCreate (NULL, pixelsWide, pixelsHigh, 8, |
0, colorSpace, |
// this will give us an optimal BGRA format for the device: |
(kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst)); |
CGColorSpaceRelease(colorSpace); |
return bitmapContext; |
} |
- (UIImage *)reflectedImage:(UIImageView *)fromImage withHeight:(NSInteger)height |
{ |
if (height == 0) |
return nil; |
// create a bitmap graphics context the size of the image |
CGContextRef mainViewContentContext = MyCreateBitmapContext(fromImage.bounds.size.width, height); |
// create a 2 bit CGImage containing a gradient that will be used for masking the |
// main view content to create the 'fade' of the reflection. The CGImageCreateWithMask |
// function will stretch the bitmap image as required, so we can create a 1 pixel wide gradient |
CGImageRef gradientMaskImage = CreateGradientImage(1, height); |
// create an image by masking the bitmap of the mainView content with the gradient view |
// then release the pre-masked content bitmap and the gradient bitmap |
CGContextClipToMask(mainViewContentContext, CGRectMake(0.0, 0.0, fromImage.bounds.size.width, height), gradientMaskImage); |
CGImageRelease(gradientMaskImage); |
// In order to grab the part of the image that we want to render, we move the context origin to the |
// height of the image that we want to capture, then we flip the context so that the image draws upside down. |
CGContextTranslateCTM(mainViewContentContext, 0.0, height); |
CGContextScaleCTM(mainViewContentContext, 1.0, -1.0); |
// draw the image into the bitmap context |
CGContextDrawImage(mainViewContentContext, fromImage.bounds, fromImage.image.CGImage); |
// create CGImageRef of the main view bitmap content, and then release that bitmap context |
CGImageRef reflectionImage = CGBitmapContextCreateImage(mainViewContentContext); |
CGContextRelease(mainViewContentContext); |
// convert the finished reflection image to a UIImage |
UIImage *theImage = [UIImage imageWithCGImage:reflectionImage]; |
// image is retained by the property setting above, so we can release the original |
CGImageRelease(reflectionImage); |
return theImage; |
} |
#pragma mark - UITableViewDelegate |
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section |
{ |
return 0.0; |
} |
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath |
{ |
return 40.0; |
} |
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section |
{ |
return 2; |
} |
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath |
{ |
SliderCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellID]; |
UISlider *slider = (UISlider *)[cell.contentView viewWithTag:kSliderTag]; |
if (indexPath.row == 0) |
{ |
cell.textLabel.text = @"Size"; |
slider.value = kDefaultReflectionFraction; |
[slider addTarget:self action:@selector(sizeSlideAction:) forControlEvents:UIControlEventValueChanged]; |
cell.detailTextLabel.text = [NSString stringWithFormat:@"%0.2f", slider.value]; |
} |
else |
{ |
cell.textLabel.text = @"Alpha"; |
slider.value = kDefaultReflectionOpacity; |
[slider addTarget:self action:@selector(alphaSlideAction:) forControlEvents:UIControlEventValueChanged]; |
cell.detailTextLabel.text = [NSString stringWithFormat:@"%0.2f", slider.value]; |
} |
return cell; |
} |
@end |
Copyright © 2015 Apple Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2015-09-24