I am using this function for rendering MKMapView instance into image:
#implementation UIView (Ext)
- (UIImage*) renderToImage
{
UIGraphicsBeginImageContext(self.frame.size);
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
This works fine. But with iphone4 the rendered image doesn't have same resolution as it has really on device. On device I have the 640x920 map view quality, and rendered image has the resolution 320x460.
Then I doubled the size that is provided to UIGraphicsBeginImageContext() function but that filled the only top-left image part.
Question: Is there any way to get map rendered to image with full resolution 640x920?
Try using UIGraphicsBeginImageContextWithOptions instead of UIGraphicsBeginImageContext:
UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, 0.0);
See QA1703 for more details. It says:
Note: Starting from iOS 4,
UIGraphicsBeginImageContextWithOptions
allows you to provide with a scale
factor. A scale factor of zero sets it
to the scale factor of the device's
main screen. This enables you to get
the sharpest, highest-resolustion
snapshot of the display, including a
Retina Display.
iOS 7 introduced a new method to generate screenshots of a MKMapView. It is now possible to use the new MKMapSnapshot API as follows:
MKMapView *mapView = [..your mapview..]
MKMapSnapshotOptions *options = [[MKMapSnapshotOptions alloc]init];
options.region = mapView.region;
options.mapType = MKMapTypeStandard;
options.showsBuildings = NO;
options.showsPointsOfInterest = NO;
options.size = CGSizeMake(1000, 500);
MKMapSnapshotter *snapshotter = [[MKMapSnapshotter alloc]initWithOptions:options];
[snapshotter startWithQueue:dispatch_get_main_queue() completionHandler:^(MKMapSnapshot *snapshot, NSError *error) {
if( error ) {
NSLog( #"An error occurred: %#", error );
} else {
[UIImagePNGRepresentation( snapshot.image ) writeToFile:#"/Users/<yourAccountName>/map.png" atomically:YES];
}
}];
Currently all overlays and annotations are not rendered. You have to render them afterwards onto the resulting snapshot image yourself. The provided MKMapSnapshot object has a handy helper method to do the mapping between coordinates and points:
CGPoint point = [snapshot pointForCoordinate:locationCoordinate2D];
Related
I have scenario, in which I am getting images using Web Service and all images are in different resolution. Now my requirement is that I want resolution of each Images and using that I want to define size of UIImageView so I can prevent my Images from getting blurred
For example image resolution if 326 pixel/inch the imageview should be as size of that image can represent fully without any blur.
UIImage *img = [UIImage imageNamed:#"foo.png"];
CGRect rect = CGRectMake(0, 0, img.size.width, img.size.height);
UIImageView *imgView = [[UIImageView alloc] initWithFrame:rect];
[imgView setImage:img];
Image size IS it's resolution.
Your problem might be - retina display!
Check for Retina display and thus - make UIImageView width/height twice smaller (so that each UIImageView pixel would consist of four smaller UIImage pixels for retina display).
How to check for retina display:
https://stackoverflow.com/a/7607087/894671
How to check image size (without actually loading image in memory):
NSString *mFullPath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]
stringByAppendingPathComponent:#"imageName.png"];
NSURL *imageFileURL = [NSURL fileURLWithPath:mFullPath];
CGImageSourceRef imageSource = CGImageSourceCreateWithURL((CFURLRef)imageFileURL, NULL);
if (imageSource == NULL)
{
// Error loading image ...
}
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:NO], (NSString *)kCGImageSourceShouldCache, nil];
CFDictionaryRef imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, (CFDictionaryRef)options);
NSNumber *mImgWidth;
NSNumber *mImgHeight;
if (imageProperties)
{
//loaded image width
mImgWidth = (NSNumber *)CFDictionaryGetValue(imageProperties, kCGImagePropertyPixelWidth);
//loaded image height
mImgHeight = (NSNumber *)CFDictionaryGetValue(imageProperties, kCGImagePropertyPixelHeight);
CFRelease(imageProperties);
}
if (imageSource != NULL)
{
CFRelease(imageSource);
}
So - for example:
UIImageView *mImgView = [[UIImageView alloc] init];
[mImgView setImage:[UIImage imageNamed:#"imageName.png"]];
[[self view] addSubview:mImgView];
if ([UIScreen instancesRespondToSelector:#selector(scale)])
{
CGFloat scale = [[UIScreen mainScreen] scale];
if (scale > 1.0)
{
//iphone retina screen
[mImgView setFrame:CGRectMake(0,0,[mImgWidth intValue]/2,[mImgHeight intValue]/2)];
}
else
{
//iphone screen
[mImgView setFrame:CGRectMake(0,0,[mImgWidth intValue],[mImgHeight intValue])];
}
}
Hope that helps!
You can get image size using following code. So, first calculate downloaded image size and than make image view according to that.
UIImage *Yourimage = [UIImage imageNamed:#"image.png"];
CGFloat width = Yourimage.size.width;
CGFloat height = Yourimage.size.height;
Hope, this will help you..
UIImage *oldimage = [UIImage imageWithContentsOfFile:imagePath]; // or you can set from url with NSURL
CGSize imgSize = [oldimage size];
imgview.frame = CGRectMake(10, 10, imgSize.width,imgSize.height);
[imgview setImage:oldimage];
100% working ....
To solve this problem, we need to take care of the device's display resolution..
For example you have an image of resolution 326ppi which is same as of iPhone4, iPhone4S and iPod 4th Gen. So you can simply use solutions suggested by #Nit and #Peko. But for other devices(or for image with different resolution on these devices) you will need to apply maths to calculate size for better display.
Now suppose you have 260ppi(with dimensions W x H) image and you wish to display it on iPhone4S, so as the information contained in it per inches is less than the display resolution of iPhone so we will need to resize it by reducing image size by 326/260 factor. so now the size for imageView that you will use is
imageViewWidth = W*(260/326);
imageViewHeight = H*(260/326);
In general:
resizeFactor = imageResolution/deviceDisplayResolution;
imageViewWidth = W*resizeFactor;
imageViewHeight = H*resizeFactor;
Here I am considering when we set an image in imageView and resize it, it does not removes or adds pixels from image,
Let the UIImageView do the work by utilizing the contentMode property to do your image resizing for you.
You probably want to be displaying your UIImageView with a static sizing (the "frame" property) that represents the maximum size of the image you want to display, and allowing the images to resize within that frame relative to their own particular size requirements (overall size, aspect ratio, etc.). You can let the UIImageView do the heavy lifting for you of dealing with different sized images by mastering the contentMode property. It has many different settings, one of which is UIViewContentModeScaleAspectFit, which will downsize your image as necessary to fit within the UIImageView, which if the image is smaller, it will simply display centered. You can play with the setting to get the results you want.
Note that with this approach, there is nothing special you need to do to deal with scaling issues associated with a Retina display.
As per the requirement you stated in the question body, I believe you need not change UIImageView size.
Image can represent fully without any blur using this line of code:
imageView.contentMode = UIViewContentModeScaleAspectFit;
I have a blog application that I'm making. To compose a new entry, there is a "Compose Entry" view where the user can select a photo and input text. For the photo, there is a UIImageView placeholder and upon clicking this, a custom ImagePicker comes up where the user can select up to 3 photos.
This is where the problem comes in. I don't need the full resolution photo from the ALAsset, but at the same time, the thumbnail is too low resolution for me to use.
So what I'm doing at this point is resizing the fullResolution photos to a smaller size. However, this takes some time, especially when resizing up to 3 photos to a smaller size.
Here is a code snipped to show what I'm doing:
ALAssetRepresentation *rep = [[dict objectForKey:#"assetObject"] defaultRepresentation];
CGImageRef iref = [rep fullResolutionImage];
if (iref)
{
CGRect screenBounds = [[UIScreen mainScreen] bounds];
UIImage *previewImage;
UIImage *largeImage;
if([rep orientation] == ALAssetOrientationUp) //landscape image
{
largeImage = [[UIImage imageWithCGImage:iref] scaledToWidth:screenBounds.size.width];
previewImage = [[UIImage imageWithCGImage:iref] scaledToWidth:300];
}
else // portrait image
{
previewImage = [[[UIImage imageWithCGImage:iref] scaledToHeight:300] imageRotatedByDegrees:90];
largeImage = [[[UIImage imageWithCGImage:iref] scaledToHeight:screenBounds.size.height] imageRotatedByDegrees:90];
}
}
Here, from the fullresolution image, I am creating two images: a preview image (max 300px on the long end) and a large image (max 960px or 640px on the long end). The preview image is what is shown on the app itself in the "new entry" preview. The large image is what will be used when uploading to the server.
The actual code I'm using to resize, I grabbed somewhere from here:
-(UIImage*)scaledToWidth:(float)i_width
{
float oldWidth = self.size.width;
float scaleFactor = i_width / oldWidth;
float newHeight = self.size.height * scaleFactor;
float newWidth = oldWidth * scaleFactor;
UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight));
[self drawInRect:CGRectMake(0, 0, newWidth, newHeight)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Am I doing things wrong here? As it stands, the ALAsset thumbnail is too low clarity, and at the same time, I dont need the entire full resolution. It's all working now, but the resizing takes some time. Is this just a necessary consequence?
Thanks!
It is a necessary consequence of resizing your image that it will take some amount of time. How much depends on the device, the resolution of the asset and the format of the asset. But you don't have any control over that. But you do have control over where the resizing takes place. I suspect that right now you are resizing the image in your main thread, which will cause the UI to grind to a halt while you are doing the resizing. Do enough images, and your app will appear hung for long enough that the user will just go off and do something else (perhaps check out competing apps in the App Store).
What you should be doing is performing the resizing off the main thread. With iOS 4 and later, this has become much simpler because you can use Grand Central Dispatch to do the resizing. You can take your original block of code from above and wrap it in a block like this:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
ALAssetRepresentation *rep = [[dict objectForKey:#"assetObject"] defaultRepresentation];
CGImageRef iref = [rep fullResolutionImage];
if (iref)
{
CGRect screenBounds = [[UIScreen mainScreen] bounds];
__block UIImage *previewImage;
__block UIImage *largeImage;
if([rep orientation] == ALAssetOrientationUp) //landscape image
{
largeImage = [[UIImage imageWithCGImage:iref] scaledToWidth:screenBounds.size.width];
previewImage = [[UIImage imageWithCGImage:iref] scaledToWidth:300];
}
else // portrait image
{
previewImage = [[[UIImage imageWithCGImage:iref] scaledToHeight:300] imageRotatedByDegrees:90];
largeImage = [[[UIImage imageWithCGImage:iref] scaledToHeight:screenBounds.size.height] imageRotatedByDegrees:90];
}
dispatch_async(dispatch_get_main_queue(), ^{
// do what ever you need to do in the main thread here once your image is resized.
// this is going to be things like setting the UIImageViews to show your new images
// or adding new views to your view hierarchy
});
}
});
You'll have to think about things a little differently this way. For example, you've now broken up what used to be a single step into multiple steps now. Code that was running after this will end up running before the image resize is complete or before you actually do anything with the images, so you need to make sure that you didn't have any dependencies on those images or you'll likely crash.
A late answer, but for those stumbling on this question, you might want to consider using the fullScreenImage rather than the fullResolutionImage of the defaultRepresentation. It's usually much smaller, but still large enough to maintain good quality for larger thumbnails.
I'm trying to merge two UIImageViews. The first UIImageView (theimageView) is the background, and the second UIImageView (Birdie) is an image overlaying the first UIImageView. You can load the first UIImageView from a map or take a picture. After this you can drag, rotate and scale the second UIImageView over the first one. I want the output (saved image) to look the same as what I see on the screen.
I got that working, but I get borders and the quality and size are bad. I want the size to be the same as that of the image which is chosen, and the quality to be good. Also I get a crash if I save it a second time, right after the first time.
Here is my current code:
//save actual design in photo library
- (void)captureScreen {
UIImage *myImage = [self addImage:theImageView ToImage:Birdie];
[myImage retain];
UIImageWriteToSavedPhotosAlbum(myImage, self, #selector(imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:), self);
}
- (UIImage*) addImage:(UIImage*)theimageView toImage:(UIImage*)Birdie{
CGSize size = CGSizeMake(theimageView.size.height, theimageView.size.width);
UIGraphicsBeginImageContext(size);
CGPoint pointImg1 = CGPointMake(0,0);
[theimageView drawAtPoint:pointImg1 ];
CGPoint pointImage2 = CGPointMake(0, 0);
[Birdie drawAtPoint:pointImage2 ];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
But I only get errors with this code!
Thanks in advanced!
Take a look at Drawing a PNG Image Into a Graphics Context for Blending Mode Manipulation
I've got a UIView which I'm rendering to a UIImage via the typical UIGraphicsBeginImageContextWithOptions method, using a scale of 2.0 so the image output will always be the "retina display" version of what would show up onscreen, regardless of the user's actual screen resolution.
The UIView I'm rendering contains both images and text (UIImages and UILabels). The image is appearing in the rendered UIImage at its full resolution, and looks great. But the UILabels appear to have been rasterized at a 1.0 scale and then upscaled to 2.0, resulting in blurry text.
Is there something I'm doing wrong, or is there some way to get the text to render nice and crisp at the higher scale level? Or is there some way to do this other than using the scaling parameter of UIGraphicsBeginImageContextWithOptions that would have better results? Thanks!
The solution is to change the labels's contentsScale to 2 before you draw it, then set it back immediately thereafter. I just coded up a project to verify it, and its working just fine making a 2x image in a normal retina phone (simulator). [If you have a public place I can put it let me know.]
EDIT: the extended code walks the subviews and any container UIViews to set/unset the scale
- (IBAction)snapShot:(id)sender
{
[self changeScaleforView:snapView scale:2];
UIGraphicsBeginImageContextWithOptions(snapView.bounds.size, snapView.opaque, 2);
[snapView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
imageDisplay.image = img; // contentsScale
imageDisplay.contentMode = UIViewContentModeScaleAspectFit;
[self changeScaleforView:snapView scale:1];
}
- (void)changeScaleforView:(UIView *)aView scale:(CGFloat)scale
{
[aView.subviews enumerateObjectsUsingBlock:^void(UIView *v, NSUInteger idx, BOOL *stop)
{
if([v isKindOfClass:[UILabel class]]) {
v.layer.contentsScale = scale;
} else
if([v isKindOfClass:[UIImageView class]]) {
// labels and images
// v.layer.contentsScale = scale; won't work
// if the image is not "#2x", you could subclass UIImageView and set the name of the #2x
// on it as a property, then here you would set this imageNamed as the image, then undo it later
} else
if([v isMemberOfClass:[UIView class]]) {
// container view
[self changeScaleforView:v scale:scale];
}
} ];
}
Try rendering to an image with double size, and then create the scaled image:
UIGraphicsBeginImageContextWithOptions(size, NO, 1.0);
// Do stuff
UImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
newImage=[UIImage imageWithCGImage:[newImage CGImage] scale:2.0 orientation:UIImageOrientationUp];
Where:
size = realSize * scale;
I have been struggling with much the same oddities in the context of textview to PDF rendering. I found out that there are some documented properties on the CALayer objects which make up the view. Maybe setting the rasterizationScale of the relevant (sub)layer(s) helps.
I have an UIView with many UIImageViews as subviews. The app runs on iOS4 and I use images with retina display resolution (i.e. the images load with scale = 2)
I want to save the contents of the UIView ... BUT ... have the real size of the images inside. I.e. the view has size 200x200 and images with scale=2 inside, I'd like to save a resulting image of 400x400 and all the images with their real size.
Now what comes first to mind is to create a new image context and load again all images inside with scale=1 and that should do, but I was wondering if there is any more elegant way to do that? Seems like a waist of memory and processor time to reload everything again since it's already done ...
p.s. if anyone has an answer - including code would be nice
Implementation for rendering any UIView to image (working also for retina display).
helper.h file:
#interface UIView (Ext)
- (UIImage*) renderToImage;
#end
and belonging implementation in helper.m file:
#import <QuartzCore/QuartzCore.h>
#implementation UIView (Ext)
- (UIImage*) renderToImage
{
// IMPORTANT: using weak link on UIKit
if(UIGraphicsBeginImageContextWithOptions != NULL)
{
UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, 0.0);
} else {
UIGraphicsBeginImageContext(self.frame.size);
}
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
0.0 is the scale factor. The scale factor to apply to the bitmap. If you specify a value of 0.0, the scale factor is set to the scale factor of the device’s main screen.
QuartzCore.framework also should be put into the project because we are calling function on the layer object.
To enable weak link on UIKit framework, click on the project item in left navigator, click the project target -> build phases -> link binary and choose "optional" (weak) type on UIKit framework.
Here is library with similar extensions for UIColor, UIImage, NSArray, NSDictionary, ...
I've performed such thing to save the pins from the MKMapView as a PNG file (in retina display): MKPinAnnotationView: Are there more than three colors available?
Here's an extract of the crucial part that performs the saving of a UIView (theView) using its retina definition:
-(void) saveMyView:(UIView*)theView {
//The image where the view content is going to be saved.
UIImage* image = nil;
UIGraphicsBeginImageContextWithOptions(theView.frame.size, NO, 2.0);
[theView.layer renderInContext: UIGraphicsGetCurrentContext()];
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSData* imgData = UIImagePNGRepresentation(image);
NSString* targetPath = [NSString stringWithFormat:#"%#/%#", [self writablePath], #"thisismyview.png" ];
[imgData writeToFile:targetPath atomically:YES];
}
-(NSString*) writablePath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
return documentsDirectory;
}
The key is that the third parameter to UIGraphicsBeginImageContextWithOptions is the scale, which determines how the image will ultimately be written out.
If you always want the real pixel dimensions, use [[UIScreen mainScreen] scale] to get the current scale of the screen:
UIGraphicsBeginImageContextWithOptions(viewSizeInPoints, YES, [[UIScreen mainScreen] scale]);
If you use scale=1.0 on iPhone4, you will get an image with its dimension in points and the result is scaled down from the true pixel count. If you manually write the image out to a 640x960 dimension (eg: passing pixels as the first parameter), it will actually be the scaled-down image that is scaled back up which looks about as terrible as you imagine it would look.
Couldn't you just create a new graphics context at the desired size, use a CGAffineTransform to scale it down, render the root UIView's root layer, restore the context to the original size and render the image? Haven't tried this for retina content, but this seems to work well for large images that have been scaled down in UIImageViews...
something like:
CGSize originalSize = myOriginalImage.size; //or whatever
//create context
UIGraphicsBeginImageContext(originalSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context); //1 original context
// translate/flip the graphics context (for transforming from CG* coords to UI* coords
CGContextTranslateCTM(context, 0, originalSize.height);
CGContextScaleCTM(context, 1.0, -1.0);
//original image
CGContextDrawImage(context, CGRectMake(0,0,originalSize.width,originalSize.height), myOriginalImage.CGImage);
CGContextRestoreGState(context);//1 restore to original for UIView render;
//scaling
CGFloat wratio = originalSize.width/self.view.frame.size.width;
CGFloat hratio = originalSize.height/self.view.frame.size.height;
//scale context to match view size
CGContextSaveGState(context); //1 pre-scaled size
CGContextScaleCTM(context, wratio, hratio);
//render
[self.view.layer renderInContext:context];
CGContextRestoreGState(context);//1 restore to pre-scaled size;
UIImage *exportImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
Import QuartzCore (Click main project, Build Phases, import) and where you need it add:
#import <QuartzCore/QuartzCore.h>
My imageViews are properties, if your are not, ignore the .self and pass the imageViews into the function as parameters, then call renderInContext on the two images in a new UIGraphicsCurrentContext
- (UIImage *)saveImage
{
UIGraphicsBeginImageContextWithOptions(self.mainImage.bounds.size, NO, 0.0);
[self.backgroundImage.layer renderInContext:UIGraphicsGetCurrentContext()];
[self.mainImage.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *savedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return savedImage;
}