I am having some trouble with saving a PDF page as UIImage...the pdf is loaded from the internet and it has one page(original PDF has been splitted in sever)...but the converted image sometimes is cropped...sometimes it is small and leave white space when it is putted on UIImageview...
here is the code
-(UIImage *)imageFromPdf:(NSString *) pdfUrl{
NSURL *pdfUrlStr=[NSURL URLWithString:pdfUrl];
CFURLRef docURLRef=(CFURLRef)pdfUrlStr;
UIGraphicsBeginImageContext(CGSizeMake(768, 1024)); //840, 960
NSLog(#"save begin");
CGContextRef context = UIGraphicsGetCurrentContext();
//CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), CFSTR("/file.pdf"), NULL, NULL);
CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL(docURLRef);
NSLog(#"save complete");
CGContextTranslateCTM(context, 0.0, 900);//320
CGContextScaleCTM(context, 1.0, -1.0);
CGPDFPageRef page = CGPDFDocumentGetPage(pdf, 1);
CGContextSaveGState(context);
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, CGRectMake(0, 0, 768, 1024), 0, true);
CGContextConcatCTM(context, pdfTransform);
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);
UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resultingImage;
}
btw I have prepared my UIImageview by coding like this
self.PDFImageVIew.contentMode = UIViewContentModeScaleAspectFit;
self.PDFImageVIew.clipsToBounds = YES;
I just want this image perfectly fitted on UIImageview and may be its reducing the quality of image...can you have suggesion how can I keep the quality also? please help and give me some suggestion
thanks
CGContextTranslateCTM(context, 0.0, 900);//320
Here generally last parameter of translate operation should be the height of context or height of rectangle for which you creating image. So, i think it should be 1024(You have taken height of image context is 1024 so here i am assuming that status bar is not present). This may eliminate the issue of cropping. Some more things that i have noted on your code you should have to save the state of graphics before any operation on context. You have are saving it but after few operations.
Above code will try to make it height fit so if height of actual page is bigger than your context height then it will be scaled down. so you can obviously see white space around page.
One more thing if your original pdf page have white space in it then there is no way to eliminate it as far as i know.
Related
In my app, I want to high quality Image. Image is loaded from Facebook friend list. When that image is loaded in smaller size (50 * 50), its quality is fine. But when I try to get that image in bigger size(280 *280) quality of image diminished.
For round corner m doing like :
self.mImageView.layer.cornerRadius = 10.0;
self.mImageView.layer.borderColor = [UIColor blackColor].CGColor;
self.mImageView.layer.borderWidth = 1.0;
self.mImageView.layer.masksToBounds = YES;
For getting image m using following code :
self.mImageView.image = [self imageWithImage:profileImage scaledToSize:CGSizeMake(280, 280)];
- (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
UIGraphicsBeginImageContextWithOptions(newSize, YES,0.0);
CGContextRef context = CGContextRetain(UIGraphicsGetCurrentContext());
CGContextTranslateCTM(context, 0.0, newSize.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetInterpolationQuality(context, kCGInterpolationLow);
CGContextSetAllowsAntialiasing (context, TRUE);
CGContextSetShouldAntialias(context, TRUE);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, newSize.width, newSize.height),image.CGImage);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
I have checked my code several times, but could not figure out how to make image perfect. So, guys how this quality of image will be improved?
Thanx in advance...
…quality of image diminished.
The 'quality' of the image is still present. (Technically, you are introducing a small amount of error by resizing it, but that's not the real problem…)
So, you want to scale a 50x50px image to 280x280px? The information/detail does not exist in the source signal. Ideally, you would download a more appropriately sized image, for the size you want to display at.
If that's not an option, you could reduce pixelation by means of proper resampling and/or interpolation. This would simply smooth out the pixels your program magnifies by 5.6 -- the image would then look like a cross between pixelated and blurred (see CGContextSetAllowsAntialiasing, CGContextSetShouldAntialias, CGContextSetInterpolationQuality and related APIs to accomplish this using quartz).
In my app I have a method that draws a pdf into a context:
CGPDFPageRef page = CGPDFDocumentGetPage(pdf, index + 1);
CGAffineTransform transform = aspectFit(CGPDFPageGetBoxRect(page, kCGPDFTrimBox),
CGContextGetClipBoundingBox(ctx));
CGContextConcatCTM(ctx, transform);
CGContextDrawPDFPage(ctx, page);
Now in drawLayer, that is called when zooming, I do the necessary transformations and call again CGContextDrawPDFPage(ctx, page);
What happens is that a zoomed pdf is drawn on top of the first pdf, the problem is that in a particular page with only text, the back and blurred pdf is shown. That is strange, I thought that pdf page had white background and if this happens it's because the zoomed pdf on top has transparent background.
Now, to solve this how can I clear the context right before the CGContextDrawPDFPage(ctx, page) of drawLayer method? I tried:
//self.view.transform = CGAffineTransformIdentity;
//CGAffineTransform transform = CGAffineTransformIdentity;
//CGContextConcatCTM(ctx, transform);
//CGContextClearRect(ctx, layer.bounds);
Nothing works...thanks in advance
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, self.bounds);
Did you try to flush the context as below?
CGContextFlush(ctx);
How is iBooks able to create PDF page thumbnails so fast on first load? I tried using CGContext functions to draw the page and then resize it to get a thumbnail. But this approach takes way to long. Is there an efficient way to get thumbnails of PDF pages?
Thanks in advance,
Anupam
First get all your PDF files Path in an array[here ie:pdfs].Then if you want to show all these PDF thumbnails in UICollectionView,just pass the index obtained from the collection view Delegate Method "CellForRowAtIndexPath" to the following,
-(UIImage *)GeneratingIcon:(int)index
{
NSURL* pdfFileUrl = [NSURL fileURLWithPath:[pdfs objectAtIndex:index]];
CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL((__bridge CFURLRef)pdfFileUrl);
CGPDFPageRef page;
CGRect aRect = CGRectMake(0, 0, 102, 141); // thumbnail size
UIGraphicsBeginImageContext(aRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
UIImage* IconImage;
CGContextSaveGState(context);
CGContextTranslateCTM(context, 0.0, aRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetGrayFillColor(context, 1.0, 1.0);
CGContextFillRect(context, aRect);
// Grab the first PDF page
page = CGPDFDocumentGetPage(pdf, 1);
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFMediaBox, aRect, 0, true);
// And apply the transform.
CGContextConcatCTM(context, pdfTransform);
CGContextDrawPDFPage(context, page);
// Create the new UIImage from the context
IconImage = UIGraphicsGetImageFromCurrentImageContext();
CGContextRestoreGState(context);
UIGraphicsEndImageContext();
CGPDFDocumentRelease(pdf);
return IconImage;
}
Hope this would be fast enough to create thumbnail images for the PDF.
Disclaimer: I have not checked if this is faster or not.
There are some built in methods in ImageIO that are specialized in creating thumbnails. These methods should be optimized for creating thumbnails. You would need to add ImageIO.framework to your project and #import <ImageIO/ImageIO.h> in your code.
// Get PDF-data
NSData *pdfData = [NSData dataWithContentsOfURL:myFileURL];
// Get reference to the source
// NOTE: You are responsible for releasing the created image source
CGImageSourceRef imageSourceRef = CGImageSourceCreateWithData((__bridge CFDataRef)pdfData, NULL);
// Configure how to create the thumbnail
// NOTE: You should change the thumbnail size depending on how large thumbnails you need.
// 512 pixels is probably way too big. Smaller sizes will be faster.
NSDictionary* thumbnailOptions =
#{(id)kCGImageSourceCreateThumbnailWithTransform: (id)kCFBooleanTrue,
(id)kCGImageSourceCreateThumbnailFromImageIfAbsent: (id)kCFBooleanTrue,
(id)kCGImageSourceThumbnailMaxPixelSize: #512}; // no more than 512 px wide or high
// Create thumbnail
// NOTE: You are responsible for releasing the created image
CGImageRef imageRef =
CGImageSourceCreateThumbnailAtIndex(imageSourceRef,
0, // index 0 of the source
(__bridge CFDictionaryRef)thumbnailOptions);
// Do something with the thumbnail ...
// Release the imageRef and imageSourceRef
CGImageRelease (imageRef);
CFRelease(imageSourceRef);
I'm trying to add a png image as a custom map using MKOverlayView. I'm almost there - I am able to get the image lined up in the right place, and I know that the -drawMapRect: method in the subclass of MKOverlayView is being called periodically; I just can't seem to get the image to render properly. It's totally blurry, almost beyond recognition. I also know the image is large enough (it is 1936 × 2967). Here is my code for -drawMapRect:
- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context{
// Load image from applicaiton bundle
NSString* imageFileName = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"map.jpg"];
CGDataProviderRef provider = CGDataProviderCreateWithFilename([imageFileName UTF8String]);
CGImageRef image = CGImageCreateWithJPEGDataProvider(provider, NULL, true, kCGRenderingIntentDefault);
CGDataProviderRelease(provider);
// save context before screwing with it
CGContextSaveGState(context);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetAlpha(context, 1.0);
// get the overlay bounds
MKMapRect theMapRect = [self.overlay boundingMapRect];
CGRect theRect = [self rectForMapRect:theMapRect];
// Draw image
CGContextDrawImage(context, theRect, image);
CGImageRelease(image);
CGContextRestoreGState(context);
Does anyone have a clue what's going on?
Thanks!
-Matt
I've had a similar problem. The problem was that my boundingMapRect was defined incorrectly. The full image is rendered scaled down when the scale is small on a tile. Then the map is zoomed and not all the image tiles are in the boundingMapRect tiles so they are not redrawn in the correct scale and the scaled down version is zoomed. At least that's what I think happens.
Hope this helps.
Get rid of CGContextScaleCTM(context, 1.0, -1.0); and do a vertical flip on your image in preview instead. the mapkit seems to use the context information to determine which part of the image to render more clearly. Know it's been a while, but hope it helps!
Thanks Rob, you made my day. My blur overlay image got sharpen when I replaced
CGContextScaleCTM(context, 1.0, -1.0);
with
CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, theRect.size.height);
CGContextConcatCTM(context, flipVertical);
I am just starting to build an app that will display PDF documents. I've been experimenting, subclassing UIView and using the code from Apples demo. I have a PDF document that contains an image that is 1024 x 748 pixels at 131 ppi, so that it SHOULD fill the iPad screen in landscape view.
When I run the app the pdf is scaled to approximately .25% of its full size, centered in the iPad screen. Why isn't the PDF being displayed full sized?
Code from my custom UIView:
-(id)initWithFrame:(CGRect)frame PDFName:(NSString *)pdfName
{
self = [super initWithFrame:frame];
if(self != nil)
{
self.backgroundColor = [UIColor blueColor];
self.opaque = YES;
self.clearsContextBeforeDrawing = YES;
CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), (CFStringRef)pdfName, NULL, NULL);
pdf = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
CFRelease(pdfURL);
}
return self;
}
- (void)drawRect:(CGRect)rect {
// PDF page drawing expects a Lower-Left coordinate system, so we flip the coordinate system
// before we start drawing.
CGContextRef context = UIGraphicsGetCurrentContext();
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, kCGPDFMediaBox, 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);
}
Answer was easy. Changed the ppi of the image in the PDF to 72 ppi (still 1024 x 748). Now it fills the screen correctly. I thought that I needed to match the iPads pixel density, but I guess not.
Jk