I have to develop an application which takes PDF as input, that PDF document has 200 pages. I am using UIScrollView to swipe left and right. On each swipe I am drawing a PDF document. The code is as under :
- (id)initWithFrame:(CGRect)frame content:(NSString *)aPDFPage type:(NSString *)contentType
{
if ((self = [super initWithFrame:frame]))
{
// Initialization code
self.backgroundColor = [UIColor whiteColor];
pageRef = [[NSString alloc]initWithString:aPDFPage];
pageTypeRef = [[NSString alloc]initWithString:contentType];
}
return self;
}
- (void)drawRect:(CGRect)rect
{
ctx = UIGraphicsGetCurrentContext();
[self drawPDF];
}
-(void)drawPDF
{
NSString *pathToPdfDoc = [[NSBundle mainBundle] pathForResource:self.pageRef ofType:self.pageTypeRef];
NSURL *pdfUrl = [NSURL fileURLWithPath:pathToPdfDoc];
document = CGPDFDocumentCreateWithURL((CFURLRef)pdfUrl);
page = CGPDFDocumentGetPage(document, 1);
CGContextTranslateCTM(ctx, 0.0, [self bounds].size.height);
CGContextScaleCTM(ctx, 1.0, -1.0);
CGAffineTransform transform = aspectFit(CGPDFPageGetBoxRect(page, kCGPDFTrimBox),CGContextGetClipBoundingBox(ctx));
CGContextConcatCTM(ctx, transform);
CGContextSetInterpolationQuality(ctx, kCGInterpolationLow);
CGContextSetRenderingIntent(ctx, kCGRenderingIntentDefault);
CGContextDrawPDFPage(ctx, page);
CGPDFDocumentRelease(document);
}
-(void)dealloc
{
[pageRef release];
[pageTypeRef release];
[super dealloc];
}
This works fine. But if I swipe very fast, more often subsequent pages does not load instantly. Screen becomes white.
How to solve this, please guide.
Regards,
Ranjan
one of the obvious issues is that drawRect may be called regularly, and may only request that you draw some of the view's rect.
in your implementation, you:
read the pdf from disk. this takes a lot of time, especially since drawRect may be called at a high frequency.
read the pdf. this takes some time -- it can be avoided from occurring during drawRect.
draw one page. draw only what you need to draw, where possible.
dispose of the pdf. you should hold on to the pdf document while the pdf view is visible, rather than reading it from disk every time you need to draw.
Have a look at this thread: Fast and Lean PDF Viewer for iPhone / iPad / iOs - tips and hints?
Related
Generate PDF from UIView by rendering looses quality iOS
I have a custom UIView called TTT_WantsToBeRazorSharpView.
This view does nothing, but draw a text with
NSString*txtPleaseHelp = NSLocalizedString(#"Hello, am I blurry again?",#"");
CGContextShowTextAtPoint(ctx, 10, 50, [txtPleaseHelp cStringUsingEncoding:NSMacOSRomanStringEncoding], [txtPleaseHelp length]);
Now the View is drawn three times to an UIViewController (one time in IB) and two times in code with these lines (compare to image below):
TTT_WantsToBeRazorSharpView *customViewSharp = [[TTT_WantsToBeRazorSharpView alloc] initWithFrame:CGRectMake(10,250, 300, 80)];
[self.view addSubview:customViewSharp];
TTT_WantsToBeRazorSharpView *customViewBlurryButIKnowWhy = [[TTT_WantsToBeRazorSharpView alloc] initWithFrame:CGRectMake(361.5, 251.5, 301.5, 80.5)];
[self.view addSubview:customViewBlurryButIKnowWhy];
the first code drawn view is razorsharp, while the second isn't, but that is ok, because of rect's comma values (361.5, 251.5, 301.5, 80.5).
See this picture:
But my problem is now, if I render the view into an pdf document it is blurry!
And don't know why, see here:
and the PDF file itself Test.pdf
https://raw.github.com/florianbachmann/GeneratePDFfromUIViewButDontWantToLooseQuality/master/Test.pdf
and the lines to render the view into the pdf:
//this is blurry, but why? it can't be the comma coordinates
CGRect customFrame1 = CGRectMake(10,50, 300, 80);
TTT_WantsToBeRazorSharpView *customViewSharp = [[TTT_WantsToBeRazorSharpView alloc] initWithFrame:customFrame1];
CGContextSaveGState(context);
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, (int)customFrame1.origin.x, (int)customFrame1.origin.y);
[customViewSharp.layer renderInContext:context];
CGContextRestoreGState(context);
So why is the renderInContext:context text blurry?
I appreciate all your hints and help, I even made an GitHub project for the brave of you (with source): https://github.com/florianbachmann/GeneratePDFfromUIViewButDontWantToLooseQuality
Try this:
- (void)initValues {
UIColor *gray = [UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.3f];
CALayer *l = [self layer];
l.masksToBounds = YES;
l.cornerRadius = 10.0f;
l.borderWidth = 3.0f;
self.backgroundColor = gray;
l.backgroundColor = gray.CGColor;
l.borderColor = gray.CGColor;
}
- (void)drawRect:(CGRect)rect {
NSLog(#"TTT_WantsToBeRazorSharpView drawRect[%3.2f,%3.2f][%3.2f,%3.2f]",rect.origin.x,rect.origin.y,rect.size.width,rect.size.height);
// get the graphic context
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetShouldSmoothFonts(ctx,YES);
CGColorRef colorWhite = CGColorRetain([UIColor redColor].CGColor);
CGContextSetFillColorWithColor(ctx, colorWhite);
CGContextSelectFont(ctx, "Helvetica-Bold", 24, kCGEncodingMacRoman);
CGAffineTransform tranformer = CGAffineTransformMakeScale(1.0, -1.0);
CGContextSetTextMatrix(ctx, tranformer);
//why is this sucker blurry?
NSString*txtPleaseHelp = NSLocalizedString(#"Hello, am I blurry again?",#"");
CGContextShowTextAtPoint(ctx, 10, 50, [txtPleaseHelp cStringUsingEncoding:NSMacOSRomanStringEncoding], [txtPleaseHelp length]);
CGColorRelease(colorWhite);
}
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
if (!layer.shouldRasterize && !CGRectIsEmpty(UIGraphicsGetPDFContextBounds())) {
[self drawRect:self.bounds];
}
else {
[super drawLayer:layer inContext:ctx];
}
}
I had to change the text color to red to make it visible. Because the text is written first, then the transparent grey button is placed over it, it would make the white text disappear. When adding the drawLayer method, everything that does not need to be rasterized is written as vector to pdf, making the text also selectable.
The text in the view is rendered as bitmap in the PDF and not as vector graphics and this causes the blurry appearance. My guess is iOS rendering engine draws the text on an intermediary bitmap (for color composition purposes I think) and then this bitmap is rendered on the target context.
I have used the following command to fix blurry text:
self.frame = CGRectIntegral(self.frame);
The reason for blurry text was that alignment was not ideal, i.e. fraction values in the point coordinates, so the text appear blurry due to excessive antialiasing.
I am relatively new to programming on the iPad and I was trying to put together a simple program. Basically, it's a children's book and I need the functionality of a comic book style (or photo) viewer, where people swipe to change "pages" (or images).
Each image is 1024x768. Currently, they are stored as JPGs because of the very large file sizes PNGs seem to produce. For this story, there are 28 pages.
I took a look at the PageControl example, implementing a UIScrollView. On initialization, I create a big enough scrollview area. Then as the user scrolls, I load in the previous and next images. Again, just like the example only without implementing the page control at the bottom.
The problem I am running into is a very slight pause in the animation when I am flipping. Once the images are loaded or cached, this doesn't happen. Now, I know the photo application doesn't do this and I'm not sure what is causing it.
Here is my code for the scrollViewDidScroll method. I keep up with the page number and it will only call the loadPageIntoScrollView when a page has changed - I was thinking that the insane number of calls it was making was causing the slight pause in animation, but it turned out not to be the case.
- (void) scrollViewDidScroll: (UIScrollView *) sender
{
CGFloat pageWidth = scrollView.frame.size.width;
int localPage = floor( (scrollView.contentOffset.x - pageWidth / 2 ) / pageWidth ) + 1;
if( localPage != currentPage )
{
currentPage = localPage;
[self loadPageIntoScrollView:localPage - 1];
[self loadPageIntoScrollView:localPage];
[self loadPageIntoScrollView:localPage + 1];
}
} // scrollViewDidScroll
And here is my loadPageIntoScrollView method. I'm only creating a UIImageView and loading an image into that - I don't see how that could be much "leaner". But somehow it's causing the pause. Again, it's not a HUGE pause, just one of those things you notice and is enough to make the scrolling look like it has a very. very slight hiccup.
Thank you in advance for any help you could provide.
- (void) loadPageIntoScrollView: (int)page
{
if( page < 0 || page >= kNumberOfPages )
return;
UIImageView *controller = [pages objectAtIndex:page];
NSLog( #"checking pages" );
if( (NSNull *)controller == [NSNull null] )
{
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleSingleTap:)];
NSString *pageName = [[NSString alloc] initWithFormat:#"%d.jpg", page];
controller = [[UIImageView alloc]initWithImage:[UIImage imageNamed:pageName]];
[controller setUserInteractionEnabled:YES];
[controller addGestureRecognizer:singleTap];
[pages replaceObjectAtIndex:page withObject:controller];
[controller release];
} // if controller == null
// add the page to the scrollview
if( controller.superview == nil )
{
NSLog(#"superview was nil, adding page %d", page );
CGRect frame = scrollView.frame;
frame.origin.x = frame.size.width * page;
frame.origin.y = 0;
controller.frame = frame;
[scrollView addSubview:controller];
} // if
} // loadPageIntoScrollView
Since you say after an image is loaded in it no longer lags, I'd suspect that it is disk access that is causing your lag, but you should run your app through instruments to try to rule out cpu-spikes as well as evaluate file system usage. You may try to pre-load images to the left and right of whatever image you are on so that the user doesn't perceive as much lag.
First off, you should be able to use PNG's just fine. I have build several apps that do exactly what you are doing here, you can fit 3 1024 x 768 PNGs in memory without running out (but you can't do much more). You should also use PNG's as they are the preferred format for iOS as they are optimized when the app is bundled together during build.
The slight lag is caused by loading the image, in this line:
controller = [[UIImageView alloc]initWithImage:[UIImage imageNamed:pageName]];
What I usually do is load the images in a separate thread, using something like this:
[self performSelectorInBackground:#selector(loadPageIntoScrollView:) withObject:[NSNumber numberWithInt:localPage]];
Note that you need to put your localPage integer into a NSNumber object to pass it along, so don't forget to change your loadPageIntoScrollView: method:
- (void) loadPageIntoScrollView: (NSNumber *)pageNumber
{
int page = [pageNumber intValue];
....
Is is possible to stop CATiledLayer to draw (drawLayer:inContext)?
It draws asynchronously and when i try to release CGPDFDocumentRef, which is used by CATiledLayer, the app crashes (EXC_BAD_ACCESS).
That's my view:
#implementation TiledPDFView
- (id)initWithFrame:(CGRect)frame andScale:(CGFloat)scale{
if ((self = [super initWithFrame:frame])) {
CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];
tiledLayer.levelsOfDetail = 4;
tiledLayer.levelsOfDetailBias = 4;
tiledLayer.tileSize = CGSizeMake(512.0, 512.0);
myScale = scale;
}
return self;
}
// Set the layer's class to be CATiledLayer.
+ (Class)layerClass {
return [CATiledLayer class];
}
- (void)stopDrawing{
CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];
[tiledLayer removeFromSuperlayer];
tiledLayer.delegate = nil;
}
// Set the CGPDFPageRef for the view.
- (void)setPage:(CGPDFPageRef)newPage
{
CGPDFPageRelease(self->pdfPage);
self->pdfPage = CGPDFPageRetain(newPage);
//self->pdfPage = newPage;
}
-(void)drawRect:(CGRect)r
{
}
// Draw the CGPDFPageRef into the layer at the correct scale.
-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context
{
// First fill the background with white.
CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
CGContextFillRect(context,self.bounds);
CGContextSaveGState(context);
// Flip the context so that the PDF page is rendered
// right side up.
CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Scale the context so that the PDF page is rendered
// at the correct size for the zoom level.
CGContextScaleCTM(context, myScale,myScale);
CGContextDrawPDFPage(context, pdfPage);
CGContextRestoreGState(context);
}
// Clean up.
- (void)dealloc {
CGPDFPageRelease(pdfPage);
[super dealloc];
}
And this is where i try to stop and release PDF in view controller:
v is instance of TiledPDFView
-(void) stopDwaring {
[v stopDrawing];
[v removeFromSuperview];
[v release];
[self.view removeFromSuperview];
self.view = nil;
CGPDFDocumentRelease(pdf);
}
this post helped me solving my own trouble with CATiledLayer. I used TiledPDFview.m from Apple's documentation as example.
Since I need to redraw the entire view and all tiles at some point, I use a CATiledLayer as property.
When exiting and deallocating the viewcontroller, it crashed with [CATiledLayer retain]: Message sent to deallocated instance.
Here is my dealloc method of the view controller:
- (void)dealloc {
self.tiledLayer.contents=nil;
self.tiledLayer.delegate=nil;
[self.tiledLayer removeFromSuperlayer];
// note: releasing the layer still crashes-
// I guess removeFromSuperlayer releases it already,
// but couldn't find documentation so far.
// So that's why it's commented out:
// [self.tiledLayer release], self.tiledLayer=nil;
//release the other viewcontroller stuff...
[super dealloc];
}
That works for me. Hope it helps someone.
Remove the CATiledLayer from its superlayer before releasing the CGPDFDocumentRef.
[yourTiledLayer removeFromSuperlayer];
Dont forget to set it's delegate to nil too.
yourTiledLayer.delegate = nil;
After that, you can safely release your CGPDFDocumentRef.
Edit after OP adds code:
Did you get pdfPage using CGPDFDocumentGetPage()? If so, you shouldn't release it, it is an autoreleased object.
Regarding how to add it as sublayer:
You don't actually need TiledPDFView. In your view controller, you can simply do this:
CATiledLayer *tiledLayer = [CATiledLayer layer];
tiledLayer.delegate = self; //sets where tiledLayer will look for drawLayer:inContext:
tiledLayer.tileSize = CGSizeMake(512.0f, 512.0f);
tiledLayer.levelsOfDetail = 4;
tiledLayer.levelsOfDetailBias = 4;
tiledLayer.frame = CGRectIntegral(CGRectMake(0.0f, 0.0f, 512.0f, 512.0f));
[self.view.layer addSublayer:tiledLayer];
Then move your drawLayer:inContext: implementation to your view controller.
Then in your view controller's dealloc, release it as:
[tiledLayer removeFromSuperlayer];
tiledLayer.delegate = nil;
CGPDFDocumentRelease(pdf);
Note that you can't do this on a UIView subclass, as the drawLayer:inContext: will conflict with the UIView's main layer.
object.layer.contents = Nil
This should wait for the thread to finish. It helped in my case.
TiledPDFView *pdfView;
In dealloc of pdfView's superview class, write below line of codes.
- (void)dealloc {
if (nil != self.pdfView.superview) {
self.pdfView.layer.delegate = nil;
[self.pdfView removeFromSuperview];
}
}
This works for me. Hope it will help.
I've had a similar problem.
I ended up setting a float variable "zoom" in my TiledPDFView which I set as the zoomScale of PDFScrollView in the UIScrollview Delegate method: scrollViewDidZoom
Then in my drawLayer method inside TiledPDFView I only called the contents of that method if the float variable "zoom" was above 2.
This fixes any issues of someone leaving the view without zooming. It may not be ideal for your case as this error still occurs if someone zooms above 2 then releases the viewcontroller quickly, but you might be able to find a similar technique to cover all bases.
It looks like you're doing the same thing I am, which is borrowing the ZoomingPDFView code and integrating it into your project. If your UIScrollView delegate methods in PDFScrollView are unchanged, you can solve your problem by just commenting both lines of your dealloc method (in TiledPDFView). That stuff should only be happening when you kill the parent view, anyway.
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..
EVERYTHING WRITTEN HERE ACTUALLY WORKS RIGHT
EXEPT FOR [UIImage imageNamed:] METHOD USAGE
Implementation
I am using model in witch you have a custom UITableViewCell with one custom UIView set up as Cell's backgroundView.
Custom UIView contains two Cell-sized images (320x80 px), one of which is 100% transparent to half of the view. All elements are set to be Opaque and have 1.0 Alpha property.
I don't reuse Cells because I failed to make them loading different images. Cell's reused one-by-one up to 9 cells overall. So I have 9 reusable Cells in memory.
Cell initWithStyle:reuseIdentifier method part:
CGRect viewFrame = CGRectMake(0.0f, 0.0f, 320.0f, 80.0f);
customCellView = [[CustomCellView alloc] initWithFrame:viewFrame];
customCellView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
[self setBackgroundView:customCellView];
CustomCellView's initialization method:
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
self.opaque = YES;
self.backgroundColor = [UIColor UICustomColor];
}
return self;
}
Images are being pre-loaded to NSMutableArray as UIImage objects from PNG files with UIImage's imageNamed: method.
They are being set in UITableViewDelegate's method tableView:cellForRowAtIndexPath: and passed through UITableViewCell with custom method to UIView.
And then drawn in UIView's drawRect: overridden method:
- (void)drawRect:(CGRect)rect {
CGRect contentRect = self.bounds;
if (!self.editing) {
CGFloat boundsX = contentRect.origin.x;
CGFloat boundsY = contentRect.origin.y;
CGPoint point;
point = CGPointMake(boundsX, boundsY);
if (firstImage) { [firstImage drawInRect:contentRect blendMode:kCGBlendModeNormal alpha:1.0f]; }
if (secondImage) { [secondImage drawInRect:contentRect blendMode:kCGBlendModeNormal alpha:1.0f]; }
}
}
As you see images are being drawn with drawInRect:blendMode:alpha: method.
Problem
Well, UITableView can't be scrolled at all, it's being struck on every cell, it's chunky and creepy.
Thoughts
Well digging sample code, stackoverflow and forums gave me thought to use OpenGL ES to pre-render images, but, really, is it that hard to make a smooth scrolling?
What's wrong with just using UIImageViews? Are they not fast enough? (They should be if you're preloading the UIImages).
One thing to note is that [UIImage imageNamed:] won't explicitly load the image data into memory. It'll give you a reference which is backed by the data on disk. You can get around this by making a call to [yourImage CGImage].