I'm trying to replicate this blurred background from Apple's publicly released iOS 7 example screen:
This question suggests applying a CI filter to the contents below, but that's a whole different approach. It's obvious that iOS 7 doesn't capture the contents of the views below, for many reasons:
Doing some rough testing, capturing a screenshot of the views below and applying a CIGaussianBlur filter with a large enough radius to mimic iOS 7's blur style takes 1-2 seconds, even on a simulator.
The iOS 7 blur view is able to blur over dynamic views, such as a video or animations, with no noticeable lag.
Can anyone hypothesize what frameworks they could be using to create this effect, and if it's possible to create a similar effect with current public APIs?
Edit: (from comment) We don't exactly know how Apple is doing it, but are there any basic assumptions we can make? We can assume they are using hardware, right?
Is the effect self-contained in each view, such that the effect doesn't actually know what's behind it? Or must, based on how blurs work, the contents behind the blur be taken into consideration?
If the contents behind the effect are relevant, can we assume that Apple is receiving a "feed" of the contents below and continuously rendering them with a blur?
Why bother replicating the effect? Just draw a UIToolbar behind your view.
myView.backgroundColor = [UIColor clearColor];
UIToolbar* bgToolbar = [[UIToolbar alloc] initWithFrame:myView.frame];
bgToolbar.barStyle = UIBarStyleDefault;
[myView.superview insertSubview:bgToolbar belowSubview:myView];
Apple released code at WWDC as a category on UIImage that includes this functionality, if you have a developer account you can grab the UIImage category (and the rest of the sample code) by going to this link: https://developer.apple.com/wwdc/schedule/ and browsing for section 226 and clicking on details. I haven't played around with it yet but I think the effect will be a lot slower on iOS 6, there are some enhancements to iOS 7 that make grabbing the initial screen shot that is used as input to the blur a lot faster.
Direct link: https://developer.apple.com/downloads/download.action?path=wwdc_2013/wwdc_2013_sample_code/ios_uiimageeffects.zip
Actually I'd bet this would be rather simple to achieve. It probably wouldn't operate or look exactly like what Apple has going on but could be very close.
First of all, you'd need to determine the CGRect of the UIView that you will be presenting. Once you've determine that you would just need to grab an image of the part of the UI so that it can be blurred. Something like this...
- (UIImage*)getBlurredImage {
// You will want to calculate this in code based on the view you will be presenting.
CGSize size = CGSizeMake(200,200);
UIGraphicsBeginImageContext(size);
[view drawViewHierarchyInRect:(CGRect){CGPointZero, w, h} afterScreenUpdates:YES]; // view is the view you are grabbing the screen shot of. The view that is to be blurred.
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Gaussian Blur
image = [image applyLightEffect];
// Box Blur
// image = [image boxblurImageWithBlur:0.2f];
return image;
}
Gaussian Blur - Recommended
Using the UIImage+ImageEffects Category Apple's provided here, you'll get a gaussian blur that looks very much like the blur in iOS 7.
Box Blur
You could also use a box blur using the following boxBlurImageWithBlur: UIImage category. This is based on an algorythem that you can find here.
#implementation UIImage (Blur)
-(UIImage *)boxblurImageWithBlur:(CGFloat)blur {
if (blur < 0.f || blur > 1.f) {
blur = 0.5f;
}
int boxSize = (int)(blur * 50);
boxSize = boxSize - (boxSize % 2) + 1;
CGImageRef img = self.CGImage;
vImage_Buffer inBuffer, outBuffer;
vImage_Error error;
void *pixelBuffer;
CGDataProviderRef inProvider = CGImageGetDataProvider(img);
CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
inBuffer.width = CGImageGetWidth(img);
inBuffer.height = CGImageGetHeight(img);
inBuffer.rowBytes = CGImageGetBytesPerRow(img);
inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);
pixelBuffer = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));
if(pixelBuffer == NULL)
NSLog(#"No pixelbuffer");
outBuffer.data = pixelBuffer;
outBuffer.width = CGImageGetWidth(img);
outBuffer.height = CGImageGetHeight(img);
outBuffer.rowBytes = CGImageGetBytesPerRow(img);
error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
if (error) {
NSLog(#"JFDepthView: error from convolution %ld", error);
}
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef ctx = CGBitmapContextCreate(outBuffer.data,
outBuffer.width,
outBuffer.height,
8,
outBuffer.rowBytes,
colorSpace,
kCGImageAlphaNoneSkipLast);
CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
UIImage *returnImage = [UIImage imageWithCGImage:imageRef];
//clean up
CGContextRelease(ctx);
CGColorSpaceRelease(colorSpace);
free(pixelBuffer);
CFRelease(inBitmapData);
CGImageRelease(imageRef);
return returnImage;
}
#end
Now that you are calculating the screen area to blur, passing it into the blur category and receiving a UIImage back that has been blurred, now all that is left is to set that blurred image as the background of the view you will be presenting. Like I said, this will not be a perfect match for what Apple is doing, but it should still look pretty cool.
Hope it helps.
iOS8 answered these questions.
- (instancetype)initWithEffect:(UIVisualEffect *)effect
or Swift:
init(effect effect: UIVisualEffect)
I just wrote my little subclass of UIView that has ability to produce native iOS 7 blur on any custom view. It uses UIToolbar but in a safe way for changing it's frame, bounds, color and alpha with real-time animation.
Please let me know if you notice any problems.
https://github.com/ivoleko/ILTranslucentView
There is a rumor that Apple engineers claimed, to make this performant they are reading directly out of the gpu buffer which raises security issues which is why there is no public API to do this yet.
This is a solution that you can see in the vidios of the WWDC. You have to do a Gaussian Blur, so the first thing you have to do is to add a new .m and .h file with the code i'm writing here, then you have to make and screen shoot, use the desired effect and add it to your view, then your UITable UIView or what ever has to be transparent, you can play with applyBlurWithRadius, to archive the desired effect, this call works with any UIImage.
At the end the blured image will be the background and the rest of the controls above has to be transparent.
For this to work you have to add the next libraries:
Acelerate.framework,UIKit.framework,CoreGraphics.framework
I hope you like it.
Happy coding.
//Screen capture.
UIGraphicsBeginImageContext(self.view.bounds.size);
CGContextRef c = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(c, 0, 0);
[self.view.layer renderInContext:c];
UIImage* viewImage = UIGraphicsGetImageFromCurrentImageContext();
viewImage = [viewImage applyLightEffect];
UIGraphicsEndImageContext();
//.h FILE
#import <UIKit/UIKit.h>
#interface UIImage (ImageEffects)
- (UIImage *)applyLightEffect;
- (UIImage *)applyExtraLightEffect;
- (UIImage *)applyDarkEffect;
- (UIImage *)applyTintEffectWithColor:(UIColor *)tintColor;
- (UIImage *)applyBlurWithRadius:(CGFloat)blurRadius tintColor:(UIColor *)tintColor saturationDeltaFactor:(CGFloat)saturationDeltaFactor maskImage:(UIImage *)maskImage;
#end
//.m FILE
#import "cGaussianEffect.h"
#import <Accelerate/Accelerate.h>
#import <float.h>
#implementation UIImage (ImageEffects)
- (UIImage *)applyLightEffect
{
UIColor *tintColor = [UIColor colorWithWhite:1.0 alpha:0.3];
return [self applyBlurWithRadius:1 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil];
}
- (UIImage *)applyExtraLightEffect
{
UIColor *tintColor = [UIColor colorWithWhite:0.97 alpha:0.82];
return [self applyBlurWithRadius:1 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil];
}
- (UIImage *)applyDarkEffect
{
UIColor *tintColor = [UIColor colorWithWhite:0.11 alpha:0.73];
return [self applyBlurWithRadius:1 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil];
}
- (UIImage *)applyTintEffectWithColor:(UIColor *)tintColor
{
const CGFloat EffectColorAlpha = 0.6;
UIColor *effectColor = tintColor;
int componentCount = CGColorGetNumberOfComponents(tintColor.CGColor);
if (componentCount == 2) {
CGFloat b;
if ([tintColor getWhite:&b alpha:NULL]) {
effectColor = [UIColor colorWithWhite:b alpha:EffectColorAlpha];
}
}
else {
CGFloat r, g, b;
if ([tintColor getRed:&r green:&g blue:&b alpha:NULL]) {
effectColor = [UIColor colorWithRed:r green:g blue:b alpha:EffectColorAlpha];
}
}
return [self applyBlurWithRadius:10 tintColor:effectColor saturationDeltaFactor:-1.0 maskImage:nil];
}
- (UIImage *)applyBlurWithRadius:(CGFloat)blurRadius tintColor:(UIColor *)tintColor saturationDeltaFactor:(CGFloat)saturationDeltaFactor maskImage:(UIImage *)maskImage
{
if (self.size.width < 1 || self.size.height < 1) {
NSLog (#"*** error: invalid size: (%.2f x %.2f). Both dimensions must be >= 1: %#", self.size.width, self.size.height, self);
return nil;
}
if (!self.CGImage) {
NSLog (#"*** error: image must be backed by a CGImage: %#", self);
return nil;
}
if (maskImage && !maskImage.CGImage) {
NSLog (#"*** error: maskImage must be backed by a CGImage: %#", maskImage);
return nil;
}
CGRect imageRect = { CGPointZero, self.size };
UIImage *effectImage = self;
BOOL hasBlur = blurRadius > __FLT_EPSILON__;
BOOL hasSaturationChange = fabs(saturationDeltaFactor - 1.) > __FLT_EPSILON__;
if (hasBlur || hasSaturationChange) {
UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]);
CGContextRef effectInContext = UIGraphicsGetCurrentContext();
CGContextScaleCTM(effectInContext, 1.0, -1.0);
CGContextTranslateCTM(effectInContext, 0, -self.size.height);
CGContextDrawImage(effectInContext, imageRect, self.CGImage);
vImage_Buffer effectInBuffer;
effectInBuffer.data = CGBitmapContextGetData(effectInContext);
effectInBuffer.width = CGBitmapContextGetWidth(effectInContext);
effectInBuffer.height = CGBitmapContextGetHeight(effectInContext);
effectInBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectInContext);
UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]);
CGContextRef effectOutContext = UIGraphicsGetCurrentContext();
vImage_Buffer effectOutBuffer;
effectOutBuffer.data = CGBitmapContextGetData(effectOutContext);
effectOutBuffer.width = CGBitmapContextGetWidth(effectOutContext);
effectOutBuffer.height = CGBitmapContextGetHeight(effectOutContext);
effectOutBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectOutContext);
if (hasBlur) {
CGFloat inputRadius = blurRadius * [[UIScreen mainScreen] scale];
NSUInteger radius = floor(inputRadius * 3. * sqrt(2 * M_PI) / 4 + 0.5);
if (radius % 2 != 1) {
radius += 1;
}
vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend);
vImageBoxConvolve_ARGB8888(&effectOutBuffer, &effectInBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend);
vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend);
}
BOOL effectImageBuffersAreSwapped = NO;
if (hasSaturationChange) {
CGFloat s = saturationDeltaFactor;
CGFloat floatingPointSaturationMatrix[] = {
0.0722 + 0.9278 * s, 0.0722 - 0.0722 * s, 0.0722 - 0.0722 * s, 0,
0.7152 - 0.7152 * s, 0.7152 + 0.2848 * s, 0.7152 - 0.7152 * s, 0,
0.2126 - 0.2126 * s, 0.2126 - 0.2126 * s, 0.2126 + 0.7873 * s, 0,
0, 0, 0, 1,
};
const int32_t divisor = 256;
NSUInteger matrixSize = sizeof(floatingPointSaturationMatrix)/sizeof(floatingPointSaturationMatrix[0]);
int16_t saturationMatrix[matrixSize];
for (NSUInteger i = 0; i < matrixSize; ++i) {
saturationMatrix[i] = (int16_t)roundf(floatingPointSaturationMatrix[i] * divisor);
}
if (hasBlur) {
vImageMatrixMultiply_ARGB8888(&effectOutBuffer, &effectInBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags);
effectImageBuffersAreSwapped = YES;
}
else {
vImageMatrixMultiply_ARGB8888(&effectInBuffer, &effectOutBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags);
}
}
if (!effectImageBuffersAreSwapped)
effectImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
if (effectImageBuffersAreSwapped)
effectImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]);
CGContextRef outputContext = UIGraphicsGetCurrentContext();
CGContextScaleCTM(outputContext, 1.0, -1.0);
CGContextTranslateCTM(outputContext, 0, -self.size.height);
CGContextDrawImage(outputContext, imageRect, self.CGImage);
if (hasBlur) {
CGContextSaveGState(outputContext);
if (maskImage) {
CGContextClipToMask(outputContext, imageRect, maskImage.CGImage);
}
CGContextDrawImage(outputContext, imageRect, effectImage.CGImage);
CGContextRestoreGState(outputContext);
}
if (tintColor) {
CGContextSaveGState(outputContext);
CGContextSetFillColorWithColor(outputContext, tintColor.CGColor);
CGContextFillRect(outputContext, imageRect);
CGContextRestoreGState(outputContext);
}
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return outputImage;
}
You can find your solution from apple's DEMO in this page:
WWDC 2013 , find out and download UIImageEffects sample code.
Then with #Jeremy Fox's code. I changed it to
- (UIImage*)getDarkBlurredImageWithTargetView:(UIView *)targetView
{
CGSize size = targetView.frame.size;
UIGraphicsBeginImageContext(size);
CGContextRef c = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(c, 0, 0);
[targetView.layer renderInContext:c]; // view is the view you are grabbing the screen shot of. The view that is to be blurred.
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return [image applyDarkEffect];
}
Hope this will help you.
Here is a really easy way of doing it:https://github.com/JagCesar/iOS-blur
Just copy the layer of UIToolbar and you're done, AMBlurView does it for you.
Okay, it's not as blurry as control center, but is's blurry enough.
Remember that iOS7 is under NDA.
Every response here is using vImageBoxConvolve_ARGB8888 this function is really, really slow, that is fine, if the performance is not a high priority requirement, but if you are using this for transitioning between two View Controllers (for example) this approach means times over 1 second or maybe more, that is very bad to the user experience of your application.
If you prefer leave all this image processing to the GPU (And you should) you can get a much better effect and also awesome times rounding 50ms (supposing that you have a time of 1 second in the first approach), so, lets do it.
First download the GPUImage Framework (BSD Licensed) here.
Next, Add the following classes (.m and .h) from the GPUImage (I'm not sure that these are the minimum needed for the blur effect only)
GPUImage.h
GPUImageAlphaBlendFilter
GPUImageFilter
GPUImageFilterGroup
GPUImageGaussianBlurPositionFilter
GPUImageGaussianSelectiveBlurFilter
GPUImageLuminanceRangeFilter
GPUImageOutput
GPUImageTwoInputFilter
GLProgram
GPUImageBoxBlurFilter
GPUImageGaussianBlurFilter
GPUImageiOSBlurFilter
GPUImageSaturationFilter
GPUImageSolidColorGenerator
GPUImageTwoPassFilter
GPUImageTwoPassTextureSamplingFilter
iOS/GPUImage-Prefix.pch
iOS/GPUImageContext
iOS/GPUImageMovieWriter
iOS/GPUImagePicture
iOS/GPUImageView
Next, create a category on UIImage, that will add a blur effect to an existing UIImage:
#import "UIImage+Utils.h"
#import "GPUImagePicture.h"
#import "GPUImageSolidColorGenerator.h"
#import "GPUImageAlphaBlendFilter.h"
#import "GPUImageBoxBlurFilter.h"
#implementation UIImage (Utils)
- (UIImage*) GPUBlurredImage
{
GPUImagePicture *source =[[GPUImagePicture alloc] initWithImage:self];
CGSize size = CGSizeMake(self.size.width * self.scale, self.size.height * self.scale);
GPUImageBoxBlurFilter *blur = [[GPUImageBoxBlurFilter alloc] init];
[blur setBlurRadiusInPixels:4.0f];
[blur setBlurPasses:2.0f];
[blur forceProcessingAtSize:size];
[source addTarget:blur];
GPUImageSolidColorGenerator * white = [[GPUImageSolidColorGenerator alloc] init];
[white setColorRed:1.0f green:1.0f blue:1.0f alpha:0.1f];
[white forceProcessingAtSize:size];
GPUImageAlphaBlendFilter * blend = [[GPUImageAlphaBlendFilter alloc] init];
blend.mix = 0.9f;
[blur addTarget:blend];
[white addTarget:blend];
[blend forceProcessingAtSize:size];
[source processImage];
return [blend imageFromCurrentlyProcessedOutput];
}
#end
And last, add the following frameworks to your project:
AVFoundation
CoreMedia
CoreVideo
OpenGLES
Yeah, got fun with this much faster approach ;)
You can try using my custom view, which has capability to blur the background. It does this by faking taking snapshot of the background and blur it, just like the one in Apple's WWDC code. It is very simple to use.
I also made some improvement over to fake the dynamic blur without losing the performance. The background of my view is a scrollView which scrolls with the view, thus provide the blur effect for the rest of the superview.
See the example and code on my GitHub
Core Background implements the desired iOS 7 effect.
https://github.com/justinmfischer/core-background
Disclaimer: I am the author of this project
I have a [UIButton buttonWithType:UIButtonTypeCustom] that has an image (or a background image - same problem) created by [UIImage imageWithContentsOfFile:] pointing to a JPG file taken by the camera and saved in the documents folder by the application.
If I define the image for UIControlStateNormal only, then when I touch the button the image gets darker as expected, but it also rotates either 90 degrees or 180 degrees. When I remove my finger it returns to normal.
This does not happen if I use the same image for UIControlStateHighlighted, but then I lose the touch indication (darker image).
This only happens with an image read from a file. It does not happen with [UIImage ImageNamed:].
I tried saving the file in PNG format rather than as JPG. In this case the image shows up in the wrong orientation to begin with, and is not rotated again when touched. This is not a good solution anyhow because the PNG is far too large and slow to handle.
Is this a bug or am I doing something wrong?
I was not able to find a proper solution to this and I needed a quick workaround. Below is a function which, given a UIImage, returns a new image which is darkened with a dark alpha fill. The context fill commands could be replaced with other draw or fill routines to provide different types of darkening.
This is un-optimized and was made with minimal knowledge of the graphics api.
You can use this function to set the UIControlStateHighlighted state image so that at least it will be darker.
+ (UIImage *)darkenedImageWithImage:(UIImage *)sourceImage
{
UIImage * darkenedImage = nil;
if (sourceImage)
{
// drawing prep
CGImageRef source = sourceImage.CGImage;
CGRect drawRect = CGRectMake(0.f,
0.f,
sourceImage.size.width,
sourceImage.size.height);
CGContextRef context = CGBitmapContextCreate(NULL,
drawRect.size.width,
drawRect.size.height,
CGImageGetBitsPerComponent(source),
CGImageGetBytesPerRow(source),
CGImageGetColorSpace(source),
CGImageGetBitmapInfo(source)
);
// draw given image and then darken fill it
CGContextDrawImage(context, drawRect, source);
CGContextSetBlendMode(context, kCGBlendModeOverlay);
CGContextSetRGBFillColor(context, 0.f, 0.f, 0.f, 0.5f);
CGContextFillRect(context, drawRect);
// get context result
CGImageRef darkened = CGBitmapContextCreateImage(context);
CGContextRelease(context);
// convert to UIImage and preserve original orientation
darkenedImage = [UIImage imageWithCGImage:darkened
scale:1.f
orientation:sourceImage.imageOrientation];
CGImageRelease(darkened);
}
return darkenedImage;
}
To fix this you need additional normalization function like this:
public extension UIImage {
func normalizedImage() -> UIImage! {
if self.imageOrientation == .Up {
return self
}
UIGraphicsBeginImageContextWithOptions(self.size, false, self.scale)
self.drawInRect(CGRectMake(0, 0, self.size.width, self.size.height))
let normalized = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return normalized
}
}
then you can use it like that:
self.photoButton.sd_setImageWithURL(avatarURL,
forState: .Normal,
placeholderImage: UIImage(named: "user_avatar_placeholder")) {
[weak self] (image, error, cacheType, url) in
guard let strongSelf = self else {
return
}
strongSelf.photoButton.setImage(image.normalizedImage(), forState: .Normal
}
I am stuck with parsing a PDF file. Please guide me how to do this.
Header file.
//PDFViewer.h
#interface PDFViewer : UIView
{
CGPDFDocumentRef pdf;
}
-(void)drawInContext:(CGContextRef)context;
#end
Implementation file
//PDFViewer.m
#implementation PDFViewer
- (id)initWithFrame:(CGRect)frame
{
if ((self = [super initWithFrame:frame]))
{
// Initialization code
if(self != nil)
{
CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), CFSTR("WR1MayJun1S08.pdf"), NULL, NULL);
pdf = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
CFRelease(pdfURL);
}
}
return self;
}
-(void)drawInContext:(CGContextRef)context
{
// PDF page drawing expects a Lower-Left coordinate system, so we flip the coordinate system
// before we start drawing.
CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Grab the first PDF page
CGPDFPageRef page = CGPDFDocumentGetPage(pdf, 1);
// We're about to modify the context CTM to draw the PDF page where we want it, so save the graphics state in case we want to do more drawing
CGContextSaveGState(context);
// CGPDFPageGetDrawingTransform provides an easy way to get the transform for a PDF page. It will scale down to fit, including any
// base rotations necessary to display the PDF page correctly.
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, self.bounds, 0, true);
// And apply the transform.
CGContextConcatCTM(context, pdfTransform);
// Finally, we draw the page and restore the graphics state for further manipulations!
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);
}
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
// Drawing code
}
*/
- (void)dealloc
{
CGPDFDocumentRelease(pdf);
[super dealloc];
}
#end
Now I am adding this class (PDFViewer.h) to my MainViewController.
//MainViewController.m
CGRect frame = CGRectMake(0, 200, 300, 500);
PDFViewer *pdfViewer = [[PDFViewer alloc] initWithFrame:frame];
CGContextRef context = UIGraphicsGetCurrentContext();
[pdfViewer drawInContext:context];
[self.view addSubview:pdfViewer];
It shows nothing. I get the following errors/warnings:
local MultiView[2850] <Error>: CGContextTranslateCTM: invalid context
local MultiView[2850] <Error>: CGContextScaleCTM: invalid context
local MultiView[2850] <Error>: CGContextSaveGState: invalid context
local MultiView[2850] <Error>: CGContextConcatCTM: invalid context
local MultiView[2850] <Error>: CGContextRestoreGState: invalid context
What am I missing?
Regards.
UIGraphicsGetCurrentContext does not return a context if there isn't one, obviously.
You try to get the context at view initialization, at that time there is no context available. A valid context gets pushed onto the stack just before -[UIView drawRect:] is being called. This should work:
//PDFViewer.m
#implementation PDFViewer
- (void)drawRect:(CGRect)rect {
[self drawInContext:UIGraphicsGetCurrentContext()];
}
#end
EDIT
Eventhough I don't like to give anyone copy-and-paste-ready-code, I don't think there is another option left if you didn't understand my latest comment. I don't know what you've tried, but if you try to understand what I'm really saying, this is the only thing you can come up with:
//PDFViewer.m
#implementation PDFViewer
- (id)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame])
{
CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), CFSTR("WR1MayJun1S08.pdf"), NULL, NULL);
pdf = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
CFRelease(pdfURL);
}
return self;
}
-(void)drawInContext:(CGContextRef)context
{
// PDF page drawing expects a Lower-Left coordinate system, so we flip the coordinate system
// before we start drawing.
CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Grab the first PDF page
CGPDFPageRef page = CGPDFDocumentGetPage(pdf, 1);
// We're about to modify the context CTM to draw the PDF page where we want it, so save the graphics state in case we want to do more drawing
CGContextSaveGState(context);
// CGPDFPageGetDrawingTransform provides an easy way to get the transform for a PDF page. It will scale down to fit, including any
// base rotations necessary to display the PDF page correctly.
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, self.bounds, 0, true);
// And apply the transform.
CGContextConcatCTM(context, pdfTransform);
// Finally, we draw the page and restore the graphics state for further manipulations!
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);
}
- (void)drawRect:(CGRect)rect {
[self drawInContext:UIGraphicsGetCurrentContext()];
}
- (void)dealloc
{
CGPDFDocumentRelease(pdf);
[super dealloc];
}
#end
—
//MainViewController.m
CGRect frame = CGRectMake(0, 200, 300, 500);
PDFViewer *pdfViewer = [[PDFViewer alloc] initWithFrame:frame];
[self.view addSubview:pdfViewer];
I got another simple way to parse PDF for iPhone/iPad:
1.Take one UIwebView (name:pdfView).
2.Give IBoutlet connection to it & Delegate it to FilesOwner
3.In Viewdidload
[self.pdfView loadRequest:[NSURLRequest requestWithURL:[NSURL
fileURLWithPath:[[NSBundle mainBundle]
pathForResource:#"ObjC" ofType:#"pdf"]]]];
4.ObjC.pdf should be in resource folder..
I use the same big images in a tableView and detailView.
Need to make imageView filled in 40x40 when an imags is showed in tableView, but stretched on a half of a screen. I played with several properties but have no positive result:
[cell.imageView setBounds:CGRectMake(0, 0, 50, 50)];
[cell.imageView setClipsToBounds:NO];
[cell.imageView setFrame:CGRectMake(0, 0, 50, 50)];
[cell.imageView setContentMode:UIViewContentModeScaleAspectFill];
I am using SDK 3.0 with build in "Cell Objects in Predefined Styles".
I put Ben's code as an extension in my NS-Extensions file so that I can tell any image to make a thumbnail of itself, as in:
UIImage *bigImage = [UIImage imageNamed:#"yourImage.png"];
UIImage *thumb = [bigImage makeThumbnailOfSize:CGSizeMake(50,50)];
Here is .h file:
#interface UIImage (PhoenixMaster)
- (UIImage *) makeThumbnailOfSize:(CGSize)size;
#end
and then in the NS-Extensions.m file:
#implementation UIImage (PhoenixMaster)
- (UIImage *) makeThumbnailOfSize:(CGSize)size
{
UIGraphicsBeginImageContextWithOptions(size, NO, UIScreen.mainScreen.scale);
// draw scaled image into thumbnail context
[self drawInRect:CGRectMake(0, 0, size.width, size.height)];
UIImage *newThumbnail = UIGraphicsGetImageFromCurrentImageContext();
// pop the context
UIGraphicsEndImageContext();
if(newThumbnail == nil)
NSLog(#"could not scale image");
return newThumbnail;
}
#end
I cache a thumbnail version since using large images scaled down on the fly uses too much memory.
Here's my thumbnail code:
- (UIImage *)thumbnailOfSize:(CGSize)size {
if( self.previewThumbnail )
return self.previewThumbnail; // returned cached thumbnail
UIGraphicsBeginImageContext(size);
// draw scaled image into thumbnail context
[self.preview drawInRect:CGRectMake(0, 0, size.width, size.height)];
UIImage *newThumbnail = UIGraphicsGetImageFromCurrentImageContext();
// pop the context
UIGraphicsEndImageContext();
if(newThumbnail == nil)
NSLog(#"could not scale image");
self.previewThumbnail = newThumbnail;
return self.previewThumbnail;
}
Just make sure you properly clear the cached thumbnail if you change your original image (self.preview in my case).
I have mine wrapped in a UIView and use this code:
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.autoresizingMask = UIViewAutoresizingFlexibleWidth |UIViewAutoresizingFlexibleHeight;
[self addSubview:imageView];
imageView.frame = self.bounds;
(self is the wrapper UIView, with the dimensions I want - I use AsyncImageView).
I thought Ben Lachman's suggestion of generating thumbnails in advance rather than on the fly was smart, so I adapted his code so it could handle a whole array and to make it more portable (no hard-coded property names).
- (NSArray *)arrayOfThumbnailsOfSize:(CGSize)size fromArray:(NSArray*)original {
NSMutableArray *temp = [NSMutableArray arrayWithCapacity:[original count]];
for(UIImage *image in original){
UIGraphicsBeginImageContext(size);
[image drawInRect:CGRectMake(0,0,size.width,size.height)];
UIImage *thumb = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[temp addObject:thumb];
}
return [NSArray arrayWithArray:temp];
}
you might be able to use this?
yourTableViewController.rowImage = [UIImage imageNamed:#"yourImage.png"];
and/or
cell.image = yourTableViewController.rowImage;
and if your images are already 40x40 then you shouldn't have to worry about setting bounds and stuff... but, i'm also new to this, so, i wouldn't know, haven't played around with Table View row/cell images much
hope this helps.
I was able to make this work using interface builder and a tableviewcell. You can set the "Mode" properties for an image view to "Aspect Fit". I'm not sure how to do this programatically.
Try setting UIImageView.autoresizesSubviews and/or UIImageView.contentStretch.