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.
Related
I have an imageview, the image within this imageview is for you to choose from the photoroll. I also have a button, when you click this button, there's an image added to a view with the addSubview code. This piece of image is draggable, resizeable and rotatable.
One problem, when I finish the image I use the method drawInRect. This draws all the layers onto eachother and creates an image. However the layers are on the wrong place and are the wrong size. It's also never rotated. I don't know how to fix this, the piece of code is beneath this text. Is it possible to keep the original image size and still have the layers drawn on the same place I drag them onto the imageview, if not how do I create a new size for this and have the result I want. And how do I draw the image rotated.
UIGraphicsBeginImageContext(imageView2.image.size);
// Draw image1
[imageView2.image drawInRect:CGRectMake(0, 0, imageView2.image.size.width, imageView2.image.size.height)];
// Draw image2
for(UIImageView *viewsSub in [self.imageViewer subviews])
{
[viewsSub.image drawInRect:CGRectMake(viewsSub.frame.origin.x, viewsSub.frame.origin.y, viewsSub.frame.size.width, viewsSub.frame.size.height)];
}
UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
pld.imageChosen2 = resultingImage;
UIGraphicsEndImageContext();
So you want something like taking a "screenshot" of your actual imageview (with subviews included), don't you?
I used this piece of code to do something similar, but don't know if would work for you.
- (UIImage *)screenshot {
CGFloat scale = [UIScreen screenScale];
if(scale > 1.5) {
UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, scale);
} else {
UIGraphicsBeginImageContext(self.frame.size);
}
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return screenshot;
}
You should add this method inside your imageview (the one that contains all the subviews you're adding).
I have the following for converting a UIView to UIImage
+(UIImage*) createUIImageFromView:(UIView *)view frame:(CGRect)frame;
{
if (UIGraphicsBeginImageContextWithOptions != NULL)
{
UIGraphicsBeginImageContextWithOptions(frame.size, NO, 2.0f);
}
else
{
UIGraphicsBeginImageContext(view.frame.size);
}
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
However, I can only select the size of the image but not where in the UIView should be converted to the image. For example, if I want to convert the rectangle CGRect(10,10,20,20) only but not the entire UIView, how do I do it?
You can set the coordinate transformation matrix on your context. This allows you to change the coordinate system, so when the layer draws at (0,0), it will actually render somewhere else in the context. The functions you want to use to actually modify the CTM are documented in the Transforming User Space section of the CGContext docs.
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 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;
}
I have a grouped UITableView that contains several cells (just standard UITableViewCells), all of which are of UITableViewCellStyleSubtitle style. Bueno. However, when I insert images into them (using the provided imageView property), the corners on the left side become square.
Example Image http://files.lithiumcube.com/tableView.png
The code being used to assign the values into the cell is:
cell.textLabel.text = currentArticle.descriptorAndTypeAndDifferentiator;
cell.detailTextLabel.text = currentArticle.stateAndDaysWorn;
cell.imageView.image = currentArticle.picture;
and currentArticle.picture is a UIImage (also the pictures, as you can see, display just fine with the exception of the square corners).
It displays the same on my iPhone 3G, in the iPhone 4 simulator and in the iPad simulator.
What I'm going for is something similar to the UITableViewCells that Apple uses in its iTunes app.
Any ideas about what I'm doing wrong?
Thanks,
-Aaron
cell.imageView.layer.cornerRadius = 16; // 16 is just a guess
cell.imageView.clipsToBounds = YES;
This will round the UIImageView so it does not draw over the cell. It will also round all the corners of all your images, but that may be OK.
Otherwise, you will have to add your own image view that will just round the one corner. You can do that by setting up a clip region in drawRect: before calling super. Or just add your own image view that is not so close to the left edge.
You can add a category on UIImage and include this method:
// Return the image, but with rounded corners. Useful for masking an image
// being used in a UITableView which has grouped style
- (UIImage *)imageWithRoundedCorners:(UIRectCorner)corners radius:(CGFloat)radius {
// We need to create a CGPath to set a clipping context
CGRect aRect = CGRectMake(0.f, 0.f, self.size.width, self.size.height);
CGPathRef clippingPath = [UIBezierPath bezierPathWithRoundedRect:aRect byRoundingCorners:corners cornerRadii:CGSizeMake(radius, radius)].CGPath;
// Begin drawing
// Start a context with a scale of 0.0 uses the current device scale so that this doesn't unnecessarily drop resolution on a retina display.
// Use `UIGraphicsBeginImageContextWithOptions(aRect.size)` instead for pre-iOS 4 compatibility.
UIGraphicsBeginImageContextWithOptions(aRect.size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextAddPath(context, clippingPath);
CGContextClip(context);
[self drawInRect:aRect];
UIImage *croppedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return croppedImage;
}
Then when you're configuring your cells, in the table view controller, call something like:
if ( *SINGLE_ROW* ) {
// We need to clip to both corners
cell.imageView.image = [image imageWithRoundedCorners:(UIRectCornerTopLeft | UIRectCornerBottomLeft) radius:radius];
} else if (indexPath.row == 0) {
cell.imageView.image = [image imageWithRoundedCorners:UIRectCornerTopLeft radius:radius];
} else if (indexPath.row == *NUMBER_OF_ITEMS* - 1) {
cell.imageView.image = [image imageWithRoundedCorners:UIRectCornerBottomLeft radius:radius];
} else {
cell.imageView.image = image;
}
but replace the SINGLE_ROW etc with real logic to determine whether you've got a single row in a section, or it's the last row. One thing to note here, is that I've found (experimentally) that the radius for a group style table is 12, which works perfectly in the simulator, but not on an iPhone. I've not been able to test it on a non-retina device. A radius of 30 looks good on the iPhone 4 (so I'm wondering if this is an image scale thing, as the images I'm using are from the AddressBook, so don't have an implied scale factor). Therefore, I've got some code before this that modifies the radius...
CGFloat radius = GroupStyleTableCellCornerRadius;
if ([[UIScreen mainScreen] respondsToSelector:#selector(scale)] && [[UIScreen mainScreen] scale] == 2){
// iPhone 4
radius = GroupStyleTableCellCornerRadiusForRetina;
}
hope that helps.