I'd like to display the same UIView multiple times. At the moment, I have my drawing in a primary UIView, then copy this into an image using renderInContext: and UIGraphicsGetImageFromCurrentImageContext. Then I set the contents of the other proxy UIViews to be this image.
UIGraphicsBeginImageContext(size);
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * clonedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return [clonedImage CGImage];
I'm experiencing a bottleneck in the renderInContext: call, presumably because it has to copy the image of the view. I'm seeing hot spots in resample_byte_h_3cpp and resample_byte_v_Ncpp, but I'm not sure what these are doing.
Is it possible to display the same UIView multiple times to reduce this overhead? Or is there a more efficient way to render the image?
How about making a copy of the UIImage instead of generating new images over and over from the UIView?
//.. Create the clonedImage from UIView
CGImageRef cgImageRef = [clonedImage CGImage];
UIImage *twinImage = [[UIImage alloc] initWithCGImage:cgImageRef];
//.. Use the images
[clonedImage release]; // if needed
[twinImage release]; // if needed
Related
I load a image and create a mirror in this way:
originalImg = [UIImage imageNamed:#"ms06.png"];
mirrorImg = [UIImage imageWithCGImage:[originalImg CGImage] scale:1.0 orientation:UIImageOrientationUpMirrored];
Then I set the above UIImage object to a subclass of UIView, and override the drawRect:
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGAffineTransform t0 = CGContextGetCTM(context);
CGContextConcatCTM(context, t0);
CGContextDrawImage(context, self.bounds, [image CGImage]);
CGContextRestoreGState(context);
}
No matter which image I draw, the displayed image always be the original one, mirrored image was never displayed when set to the UIView subclass.
I'm sure that the mirrored image was set to the UIView correctly because the debug info showed that the orientation member variable equals to 4, which means "UIImageOrientationUpMirrored", while the original image equals to 0.
Does anyone could help me with this problem, thanks.
I also tried to display the mirrored image in UIImageView with setImage: and it works correctly. By the way I found that the breakpoint in drawRect was never hit when call the setImage of UIImageView, how can we define the drawing behavior(such as draw a line above the image) when loading image to the UIImageView?
You mirrow the image on UI-Level. This returns a new UIImage, but the CGImage stays the same. If you do some NSLogs, you will notice this.
You can also do transformations on UI-Level. If you use this approach, I would suggest to use originalImg.scale instead of 1.0. Then the code would work for retina and non-retina displays.
[UIImage imageWithCGImage:[originalImg CGImage] scale:originalImg.scale orientation:UIImageOrientationUpMirrored];
If you really need to mirror the CGImage, take a look at NYXImagesKit on GitHub (see UIImage+Rotating.m)
I need to read images from NSDocumentDirectory to multiple uiimageview async so it won't block the UI.
I know i can use perform selector in background to load a uiimage, but then how can i associate it with the dynamic uiimageview ?
One convenient way is to use blocks, something like:
[self loadFullImageAt:imagePath completion:^(UIIMage * image){
self.imageView.image = image;
}];
Where you would load the image as data (since UIImage otherwise loads the image data deferred - when you first access it). It's also a good idea to decompress the image while still in the background thread, so the main thread doesn't have to do it when we first use the image.
- (void)loadFullImageAt:(NSString *)imageFilePath completion:(MBLoaderCompletion)completion {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
NSData *imageData = [NSData dataWithContentsOfFile:imageFilePath];
UIImage *image = nil;
if (imageData) {
image = [[[UIImage alloc] initWithData:imageData] decodedImage];
}
dispatch_async(dispatch_get_main_queue(), ^{
completion(image);
});
});
}
The callback is defined as:
typedef void (^MBLoaderCompletion)(UIImage *image);
Here's an UIImage category that implements the decompression code:
UIIMage+Decode.h
#import <UIKit/UIKit.h>
#interface UIImage (Decode)
- (UIImage *)decodedImage;
#end
UIIMage+Decode.m
#import "UIImage+Decode.h"
#implementation UIImage (Decode)
- (UIImage *)decodedImage {
CGImageRef imageRef = self.CGImage;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL,
CGImageGetWidth(imageRef),
CGImageGetHeight(imageRef),
8,
// Just always return width * 4 will be enough
CGImageGetWidth(imageRef) * 4,
// System only supports RGB, set explicitly
colorSpace,
// Makes system don't need to do extra conversion when displayed.
kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Little);
CGColorSpaceRelease(colorSpace);
if (!context) return nil;
CGRect rect = (CGRect){CGPointZero,{CGImageGetWidth(imageRef), CGImageGetHeight(imageRef)}};
CGContextDrawImage(context, rect, imageRef);
CGImageRef decompressedImageRef = CGBitmapContextCreateImage(context);
CGContextRelease(context);
UIImage *decompressedImage = [[UIImage alloc] initWithCGImage:decompressedImageRef scale:self.scale orientation:self.imageOrientation];
CGImageRelease(decompressedImageRef);
return decompressedImage;
}
#end
The sample code provided here assumes that we're using ARC.
When you say "dynamic" UIImageView, are these programmatically created on a UIScrollView? on a UITableView? samfisher is quite right on the basic question, but the details differ a little based upon how you created the UIImageView (e.g. if UITableView, you need to make sure that the cell is still visible and hasn't been dequeued; if UIScrollView, even then you might want to only load the UIImageView if the image is still visible on the screen (esp if the images are large or numerous)).
But the basic idea is that you might do something like:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
UIImage *image = [self getTheImage];
// ok, now that you have the image, dispatch the update of the UI back to the main queue
dispatch_async(dispatch_get_main_queue(), ^{
// if the image view is still visible, update it
});
});
Note that you invoke the retrieval of the image on some background queue or thread, but make sure to update the UI back on the main thread!
If you're updating a scrollview, you might want to do some checking that the view is still visible, such as contemplated here or here. If you're updating a tableview, perhaps something like this which checks if the cell is still visible. It all depends upon what you're trying to do.
you can use NSThread/dispatch queue for creating threads which can create your UIImageView-s and loads up images in them.
Is there a way to load a picture from the library or take a new one, resize it to a smaller size to be able to edit it and then save it at the original size? I'm struggling with this and can't make it to work. I have the resize code setup like this :
firstImage = [firstImage resizedImageWithContentMode:UIViewContentModeScaleAspectFit bounds:CGSizeMake(960, 640) interpolationQuality:kCGInterpolationHigh];
and then i have an UIImageView :
[finalImage setFrame:CGRectMake(10, 100, 300, 232)];
finalImage.image = firstImage;
if I setup the CGSizeMake at the original size of the picture it is a very slow process. I saw in other apps that they work on a smaller image and the editing process is fairly quick even for effects. What's the approach on this?
You can refer to Move and Scale Demo. This is a custom control which implements Moving and scaling and cropping image which can be really helpful to you.
Also this is the most simple code for scaling images to given size. Refer to it here: Resize/Scale of an Image
You can refer to it's code here
// UIImage+Scale.h
#interface UIImage (scale)
-(UIImage*)scaleToSize:(CGSize)size;
#end
Implementation UIImage Scale Category
With the interface in place, let’s write the code for the method that will be added to the UIImage class.
// UIImage+Scale.h
#import "UIImage+Scale.h"
#implementation UIImage (scale)
-(UIImage*)scaleToSize:(CGSize)size
{
// Create a bitmap graphics context
// This will also set it as the current context
UIGraphicsBeginImageContext(size);
// Draw the scaled image in the current context
[self drawInRect:CGRectMake(0, 0, size.width, size.height)];
// Create a new image from current context
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
// Pop the current context from the stack
UIGraphicsEndImageContext();
// Return our new scaled image
return scaledImage;
}
#end
Using the UIImage Scale Method
Calling the new scale method we added to UIImage is as simple as this:
#import "UIImage+Scale.h"
...
// Create an image
UIImage *image = [UIImage imageNamed:#"myImage.png"];
// Scale the image
UIImage *scaledImage = [image scaleToSize:CGSizeMake(25.0f, 35.0f)];
Let me know if you want more help.
Hope this helps you.
I am adding 2 images to each other and wanted to know if this is a good way to do this? This code works and looked to be powerful.
So, my question really is, It this good or is there a better way?
PS: Warning code written by a designer.
Call the function:
- (IBAction) {
UIImage *MyFirstImage = UIImage imageNamed: #"Image.png"];
UIImage *MyTopImage = UIImage imageNamed: #"Image2.png"];
CGFloat yFloat = 50;
CGFloat xFloat = 50;
UIImage *newImage = [self placeImageOnImage:MyFirstImage imageOver:MyTopImage x:&xFloat y:&yFloat];
}
The Function:
- (UIImage*) placeImageOnImage:(UIImage *)image topImage:(UIImage *)topImage x:(CGFloat *)x y:(CGFloat *)y {
// if you want the image to be added next to the image make this CGSize bigger.
CGSize newSize = CGSizeMake(image.size.width,image.size.height);
UIGraphicsBeginImageContext( newSize );
[topImage drawInRect:CGRectMake(*x,*y,topImage.size.width,topImage.size.height)];
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeDestinationOver alpha:1];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Looks OK. Perhaps you don't really need the CGFloat pointers, but that's fine, too.
The main idea is correct. There is no better way to do what you want.
Minuses:
1) Consider UIGraphicsBeginImageContextWithOptions method. UIGraphicsBeginImageContext isn't good for retina.
2) Don't pass floats as pointers. Use x:(CGFloat)x y:(CGFloat)y instead
You should use the begin context version, UIGraphicsBeginImageContextWithOptions, that allows you to specify options for scale (and pass 0 as the scale) do you don't lose any quality on retina displays.
If you want one image drawn on top of another image, just draw the one in back, then the one in front, exactly as if you were using paint. There is no need to use blend modes.
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
[topImage drawInRect:CGRectMake(*x,*y,topImage.size.width,topImage.size.height)];
I want to save the content of an UiScrollView as an Image. It seems that it is not as easy as the UIImageRepresentation that can be used for Views or ImageViews, anyone an idea how to do it?
I usually use a method implemented in a category:
+ (UIImage *)screenshot:(UIView *)view {
UIGraphicsBeginImageContext(view.bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CALayer *layer = view.layer;
[layer renderInContext:context];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
but, in your case, I suppose it will not suit well if your need is to get the whole content (also the part not visible in that moment). You could change the zoom value and then take the screenshot if it's a good enough solution.