I've got a large display area that can be panned and zoomed to view different objects. The problem that I'm running into is that the quality of the PNG images UIButton becomes somewhat degraded if I'm zoomed out (however it is back to normal when I zoom back in to 100%). It almost looks as if the image becomes oversharpened. Is this something that I'm going to have to live with, or is there a way to get rid of this grainy edge effect? The aspect ratio of the images are always 1:1, by the way.
I was able to solve this by using the answer found here in my scrollViewDidEndZooming method. Here is my code:
Resize function
- (UIImage *)resizeImage:(UIImage*)image newSize:(CGSize)newSize {
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
CGImageRef imageRef = image.CGImage;
UIGraphicsBeginImageContextWithOptions(newSize, NO, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, newSize.height);
CGContextConcatCTM(context, flipVertical);
// Draw into the context; this scales the image
CGContextDrawImage(context, newRect, imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(context);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
CGImageRelease(newImageRef);
UIGraphicsEndImageContext();
return newImage;
}
ScrollView Method
(Widget is a UIViewController subclass which contains a button and a "widgetImage" which stores the full resolution of the image that the button should display)
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale
{
for(Widget *theWidget in widgets){
UIImage *newScaledImage = [self resizeImage:theWidget.widgetImage newSize:CGSizeMake(theWidget.view.frame.size.width * scale, theWidget.view.frame.size.height * scale)];
[theWidget.widgetButton setImage:newScaledImage forState:UIControlStateNormal];
// theWidget.widgetButton.currentImage = newScaledImage;
}
}
Related
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How to get UIImage from EAGLView?
So I was just wondering if anybody knows any way to save what is stored in an EAGLContext as a UIImage.
I am currently using:
UIGraphicsBeginImageContext(CGSizeMake(768, 1024));
[self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
in other apps I have and this works fine, but obviously, EAGLContext doesn't have a .layer property. I've tried casting to UIView, but that - unsurprisingly - doesn't work:
UIView *newView = [[UIView alloc] init];
newView = (UIView *)context;
I am drawing to an EAGLContext property on a UIView (technically an EAGLContext on a UIView on another UIView on a View Controller, but I figure that shouldn't make any difference) using OpenGLES 1.
If anybody knows anything about this, even if its just that I'm completely barking up an impossible tree, please let me know!
Matt
After a few days I finally got a working solution to this. There is code provided by Apple which produces an UIImage from an EAGLView. Then you simply need to flip the image vertically since UIKit is upside down. The link to the documentation where I found this method doesn't exist anymore.
Method to capture EAGLView:
-(UIImage *)drawableToCGImage
{
GLint backingWidth2, backingHeight2;
//Bind the color renderbuffer used to render the OpenGL ES view
// If your application only creates a single color renderbuffer which is already bound at this point,
// this call is redundant, but it is needed if you're dealing with multiple renderbuffers.
// Note, replace "_colorRenderbuffer" with the actual name of the renderbuffer object defined in your class.
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
// Get the size of the backing CAEAGLLayer
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth2);
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight2);
NSInteger x = 0, y = 0, width2 = backingWidth2, height2 = backingHeight2;
NSInteger dataLength = width2 * height2 * 4;
GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte));
// Read pixel data from the framebuffer
glPixelStorei(GL_PACK_ALIGNMENT, 4);
glReadPixels(x, y, width2, height2, GL_RGBA, GL_UNSIGNED_BYTE, data);
// Create a CGImage with the pixel data
// If your OpenGL ES content is opaque, use kCGImageAlphaNoneSkipLast to ignore the alpha channel
// otherwise, use kCGImageAlphaPremultipliedLast
CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGImageRef iref = CGImageCreate(width2, height2, 8, 32, width2 * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast,
ref, NULL, true, kCGRenderingIntentDefault);
// OpenGL ES measures data in PIXELS
// Create a graphics context with the target size measured in POINTS
NSInteger widthInPoints, heightInPoints;
if (NULL != UIGraphicsBeginImageContextWithOptions) {
// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
// Set the scale parameter to your OpenGL ES view's contentScaleFactor
// so that you get a high-resolution snapshot when its value is greater than 1.0
CGFloat scale = self.contentScaleFactor;
widthInPoints = width2 / scale;
heightInPoints = height2 / scale;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(widthInPoints, heightInPoints), NO, scale);
}
else {
// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
widthInPoints = width2;
heightInPoints = height2;
UIGraphicsBeginImageContext(CGSizeMake(widthInPoints, heightInPoints));
}
CGContextRef cgcontext = UIGraphicsGetCurrentContext();
// UIKit coordinate system is upside down to GL/Quartz coordinate system
// Flip the CGImage by rendering it to the flipped bitmap context
// The size of the destination area is measured in POINTS
CGContextSetBlendMode(cgcontext, kCGBlendModeCopy);
CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, widthInPoints, heightInPoints), iref);
// Retrieve the UIImage from the current context
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Clean up
free(data);
CFRelease(ref);
CFRelease(colorspace);
CGImageRelease(iref);
return image;
}
Method to flip the image vertically:
- (UIImage *)flipImageVertically:(UIImage *)originalImage
{
UIImageView *tempImageView = [[UIImageView alloc] initWithImage:originalImage];
UIGraphicsBeginImageContext(tempImageView.frame.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGAffineTransform flipVertical = CGAffineTransformMake(
1, 0, 0, -1, 0, tempImageView.frame.size.height
);
CGContextConcatCTM(context, flipVertical);
[tempImageView.layer renderInContext:context];
UIImage *flippedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
//[tempImageView release];
return flippedImage;
}
I loaded a jpg into a UIImageView. The image is oversized to the iPhone screen. How can I resize it to a specific CGRect frame?
UIImageView *uivSplash = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"iPhone-Splash.jpg"]];
[self.view addSubview:uivSplash];
A UIImageView is just a UIView, so you can change its frame property.
uivSplash.frame = CGRectMake(0, 0, width, height);
You'll want a method like the following:
CGFloat newWidth = whateverYourDesiredWidth; // someView.size.width for example
CGFloat newHeight = whateverYourDesiredHeight; // someView.size.height for example
CGSize newSize = CGSizeMake(newWidth, newHeight);
UIGraphicsBeginImageContext(newSize);
[yourLargeImage drawInRect:CGRectMake(0, 0, newWidth, newHeight)];
UIImage * newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
So this is getting your desired width and height (maybe the screen size, maybe hard-coded size, maybe a size based on a UIView) and re-drawing the image in a context that is that size.
~Good Luck
EDIT: it occurs to me I may have misunderstood your desire, so I'll also point out (as others have said) that UIImageView has properties for its image that let you fit it to size, scale to fill, retain aspect ratio, etc.
Is there any way to draw an NSImage like images in NSButtons or other cocoa interface elements?
Here are examples:
Apple uses pdf's with black icons:
If you simply want this effect to be applied when you use your own images in a button, use [myImage setTemplate:YES]. There is no built-in way to draw images with this effect outside of a button that has the style shown in your screenshots.
You can however replicate the effect using Core Graphics. If you look closely, the effect consists of a horizontal gradient, a white drop shadow and a dark inner shadow (the latter is the most difficult).
You could implement this as a category on NSImage:
//NSImage+EtchedDrawing.h:
#interface NSImage (EtchedImageDrawing)
- (void)drawEtchedInRect:(NSRect)rect;
#end
//NSImage+EtchedDrawing.m:
#implementation NSImage (EtchedImageDrawing)
- (void)drawEtchedInRect:(NSRect)rect
{
NSSize size = rect.size;
CGFloat dropShadowOffsetY = size.width <= 64.0 ? -1.0 : -2.0;
CGFloat innerShadowBlurRadius = size.width <= 32.0 ? 1.0 : 4.0;
CGContextRef c = [[NSGraphicsContext currentContext] graphicsPort];
//save the current graphics state
CGContextSaveGState(c);
//Create mask image:
NSRect maskRect = rect;
CGImageRef maskImage = [self CGImageForProposedRect:&maskRect context:[NSGraphicsContext currentContext] hints:nil];
//Draw image and white drop shadow:
CGContextSetShadowWithColor(c, CGSizeMake(0, dropShadowOffsetY), 0, CGColorGetConstantColor(kCGColorWhite));
[self drawInRect:maskRect fromRect:NSMakeRect(0, 0, self.size.width, self.size.height) operation:NSCompositeSourceOver fraction:1.0];
//Clip drawing to mask:
CGContextClipToMask(c, NSRectToCGRect(maskRect), maskImage);
//Draw gradient:
NSGradient *gradient = [[[NSGradient alloc] initWithStartingColor:[NSColor colorWithDeviceWhite:0.5 alpha:1.0]
endingColor:[NSColor colorWithDeviceWhite:0.25 alpha:1.0]] autorelease];
[gradient drawInRect:maskRect angle:90.0];
CGContextSetShadowWithColor(c, CGSizeMake(0, -1), innerShadowBlurRadius, CGColorGetConstantColor(kCGColorBlack));
//Draw inner shadow with inverted mask:
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef maskContext = CGBitmapContextCreate(NULL, CGImageGetWidth(maskImage), CGImageGetHeight(maskImage), 8, CGImageGetWidth(maskImage) * 4, colorSpace, kCGImageAlphaPremultipliedLast);
CGColorSpaceRelease(colorSpace);
CGContextSetBlendMode(maskContext, kCGBlendModeXOR);
CGContextDrawImage(maskContext, maskRect, maskImage);
CGContextSetRGBFillColor(maskContext, 1.0, 1.0, 1.0, 1.0);
CGContextFillRect(maskContext, maskRect);
CGImageRef invertedMaskImage = CGBitmapContextCreateImage(maskContext);
CGContextDrawImage(c, maskRect, invertedMaskImage);
CGImageRelease(invertedMaskImage);
CGContextRelease(maskContext);
//restore the graphics state
CGContextRestoreGState(c);
}
#end
Example usage in a view:
- (void)drawRect:(NSRect)dirtyRect
{
[[NSColor colorWithDeviceWhite:0.8 alpha:1.0] set];
NSRectFill(self.bounds);
NSImage *image = [NSImage imageNamed:#"MyIcon.pdf"];
[image drawEtchedInRect:self.bounds];
}
This would give you the following result (shown in different sizes):
You may need to experiment a bit with the gradient colors and offset/blur radius of the two shadows to get closer to the original effect.
If you don't mind calling a private API, you can let the operating system (CoreUI) do the shading for you. You need a few declarations:
typedef CFTypeRef CUIRendererRef;
extern void CUIDraw(CUIRendererRef renderer, CGRect frame, CGContextRef context, CFDictionaryRef object, CFDictionaryRef *result);
#interface NSWindow(CoreUIRendererPrivate)
+ (CUIRendererRef)coreUIRenderer;
#end
And for the actual drawing:
CGRect drawRect = CGRectMake(x, y, width, height);
CGImageRef cgimage = your_image;
CFDictionaryRef dict = (CFDictionaryRef) [NSDictionary dictionaryWithObjectsAndKeys:
#"backgroundTypeRaised", #"backgroundTypeKey",
[NSNumber numberWithBool:YES], #"imageIsGrayscaleKey",
cgimage, #"imageReferenceKey",
#"normal", #"state",
#"image", #"widget",
[NSNumber numberWithBool:YES], #"is.flipped",
nil];
CUIDraw ([NSWindow coreUIRenderer], drawRect, cg, dict, nil);
CGImageRelease (cgimage);
This will take the alpha channel of cgimage and apply the embossing effect as seen on toolbar buttons. You may or may not need the "is.flipped" line. Remove it if your result is upside-down.
There are a bunch of variations:
kCUIPresentationStateKey = kCUIPresentationStateInactive: The window is not active, the image will be lighter.
state = rollover: Only makes sense with the previous option. This means you are hovering over the image, the window is inactive, but the button is sensitive (click-through is enabled). It will become darker.
state = pressed: Occurs when the button is pressed. The icon gets slightly darker.
Bonus tip: To find out stuff like this, you can use the SIMBL plugin CUITrace. It prints out all the CoreUI invocations of a target app. This is a treasure trove if you have to draw your own native-looking UI.
Here's a much simpler solution: just create a cell and let it draw. No mucking around with private APIs or Core Graphics.
Code could look similar to the following:
NSButtonCell *buttonCell = [[NSButtonCell alloc] initImageCell:image];
buttonCell.bordered = YES;
buttonCell.bezelStyle = NSTexturedRoundedBezelStyle;
// additional configuration
[buttonCell drawInteriorWithFrame: someRect inView:self];
You can use different cells and configurations depending on the look you want to have (eg. NSImageCell with NSBackgroundStyleDark if you want the inverted look in a selected table view row)
And as a bonus, it will automatically look correct on all versions of OS X.
To get to draw correctly within any rect, the CGContextDrawImage and CGContextFillRect for the inner mask must have the origin of (0,0). then when you draw the image for the inner shadow you can then reuse the mask rect. So ends up looking like:
CGRect cgRect = CGRectMake( 0, 0, maskRect.size.width, maskRect.size.height );
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef maskContext = CGBitmapContextCreate( NULL, CGImageGetWidth( maskImage ), CGImageGetHeight( maskImage ), 8, CGImageGetWidth( maskImage ) * 4, colorSpace, kCGImageAlphaPremultipliedLast );
CGColorSpaceRelease( colorSpace );
CGContextSetBlendMode( maskContext , kCGBlendModeXOR );
CGContextDrawImage( maskContext, cgRect, maskImage );
CGContextSetRGBFillColor( maskContext, 1.0, 1.0, 1.0, 1.0 );
CGContextFillRect( maskContext, cgRect );
CGImageRef invertedMaskImage = CGBitmapContextCreateImage( maskContext );
CGContextDrawImage( context, maskRect, invertedMaskImage );
CGImageRelease( invertedMaskImage );
CGContextRelease( maskContext );
CGContextRestoreGState( context );
You also have to leave a 1px border around the outside of the image or the shadows won't work correctly.
Is there any cropping image API for objective C that crops images dynamically in Xcode project? Please provide some tricks or techniques how could I crop camera images in iPhone.
You can use below simple code to crop an image. You have to pass the image and the CGRect which is the cropping area. Here, I crop image so that I get center part of original image and returned image is square.
// Returns largest possible centered cropped image.
- (UIImage *)centerCropImage:(UIImage *)image
{
// Use smallest side length as crop square length
CGFloat squareLength = MIN(image.size.width, image.size.height);
// Center the crop area
CGRect clippedRect = CGRectMake((image.size.width - squareLength) / 2, (image.size.height - squareLength) / 2, squareLength, squareLength);
// Crop logic
CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], clippedRect);
UIImage * croppedImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return croppedImage;
}
EDIT - Swift Version
let imageView = UIImageView(image: image)
imageView.contentMode = .scaleAspectFill
imageView.clipsToBounds = true
All these solutions seem quite complicated and many of them actually degrade the quality the image.
You can do much simpler using UIImageView's out of the box methods.
Objective-C
self.imageView.contentMode = UIViewContentModeScaleAspectFill;
[self.imageView setClipsToBounds:YES];
[self.imageView setImage:img];
This will crop your image based on the dimensions you've set for your UIImageView (I've called mine imageView here).
It's that simple and works much better than the other solutions.
You can use CoreGraphics framework to cropping image dynamically.
Here is a example code part of dynamic image crop. I hope this will be helpful for you.
- (void)drawMaskLineSegmentTo:(CGPoint)ptTo withMaskWidth:(CGFloat)maskWidth inContext:(NXMaskDrawContext)context{
if (context == nil)
return;
if (context.count <= 0){
[context addObject:[NSValue valueWithCGPoint:ptTo]];
return;
}
CGPoint ptFrom = [context.lastObject CGPointValue];
UIGraphicsBeginImageContext(self.maskImage.size);
[self.maskImage drawInRect:CGRectMake(0, 0, self.maskImage.size.width, self.maskImage.size.height)];
CGContextRef graphicsContext = UIGraphicsGetCurrentContext();
CGContextSetBlendMode(graphicsContext, kCGBlendModeCopy);
CGContextSetRGBStrokeColor(graphicsContext, 1, 1, 1, 1);
CGContextSetLineWidth(graphicsContext, maskWidth);
CGContextSetLineCap(graphicsContext, kCGLineCapRound);
CGContextMoveToPoint(graphicsContext, ptFrom.x, ptFrom.y);
CGContextAddLineToPoint(graphicsContext, ptTo.x, ptTo.y);
CGContextStrokePath(graphicsContext);
self.maskImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIGraphicsBeginImageContext(self.displayableMaskImage.size);
[self.displayableMaskImage drawInRect:CGRectMake(0, 0, self.displayableMaskImage.size.width, self.displayableMaskImage.size.height)];
graphicsContext = UIGraphicsGetCurrentContext();
CGContextSetBlendMode(graphicsContext, kCGBlendModeCopy);
CGContextSetStrokeColorWithColor(graphicsContext, self.displayableMaskColor.CGColor);
CGContextSetLineWidth(graphicsContext, maskWidth);
CGContextSetLineCap(graphicsContext, kCGLineCapRound);
CGContextMoveToPoint(graphicsContext, ptFrom.x, ptFrom.y);
CGContextAddLineToPoint(graphicsContext, ptTo.x, ptTo.y);
CGContextStrokePath(graphicsContext);
self.displayableMaskImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[context addObject:[NSValue valueWithCGPoint:ptTo]];
}
Xcode 5, iOS 7, and 4-inch screen example: Here is an open source example of a
SimpleImageCropEditor (Project Zip and Source Code Example. You can load the Image Crop Editor as a Modal View Controller and reuse. Look at the code and please leave constructive comments concerning if this example code answers the question "Image Cropping API for iOS".
Demonstrates, is example source Objective-C code, use of UIImagePickerController, #protocol, UIActionSheet, UIScrollView, UINavigationController, MFMailComposeViewController, and UIGestureRecognizer.
I'm trying to overlay a custom semi-transparent image over a base image. The overlay image is stretchable and created like this:
[[UIImage imageNamed:#"overlay.png"] stretchableImageWithLeftCapWidth:5.0 topCapHeight:5.0]
Then I pass that off to a method that overlays it onto the background image for a button:
- (void)overlayImage:(UIImage *)overlay forState:(UIControlState)state {
UIImage *baseImage = [self backgroundImageForState:state];
CGRect frame = CGRectZero;
frame.size = baseImage.size;
// create a new image context
UIGraphicsBeginImageContext(baseImage.size);
// get context
CGContextRef context = UIGraphicsGetCurrentContext();
// clear context
CGContextClearRect(context, frame);
// draw images
[baseImage drawInRect:frame];
[overlay drawInRect:frame];// blendMode:kCGBlendModeNormal alpha:1.0];
// get UIImage
UIImage *overlaidImage = UIGraphicsGetImageFromCurrentImageContext();
// clean up context
UIGraphicsEndImageContext();
[self setBackgroundImage:overlaidImage forState:state];
}
The resulting overlaidImage looks mostly correct, it is the correct size, the alpha is blended correctly, etc. however it has vertical artifacts/noise.
UIImage artifacts example http://acaciatreesoftware.com/img/UIImage-artifacts.png
(example at http://acaciatreesoftware.com/img/UIImage-artifacts.png)
I tried clearing the context first and then turning off PNG compression--which reduces the artifacting some (completely on non stretched images I think).
Does anyone know a method for drawing stretchable UIImages with out this sort of artifacting happening?
So the answer is: Don't do this. Instead you can paint your overlay procedurally. Like so:
- (void)overlayWithColor:(UIColor *)overlayColor forState:(UIControlState)state {
UIImage *baseImage = [self backgroundImageForState:state];
CGRect frame = CGRectZero;
frame.size = baseImage.size;
// create a new image context
UIGraphicsBeginImageContext(baseImage.size);
// get context
CGContextRef context = UIGraphicsGetCurrentContext();
// draw background image
[baseImage drawInRect:frame];
// overlay color
CGContextSetFillColorWithColor(context, [overlayColor CGColor]);
CGContextSetBlendMode(context, kCGBlendModeSourceAtop);
CGContextFillRect(context, frame);
// get UIImage
UIImage *overlaidImage = UIGraphicsGetImageFromCurrentImageContext();
// clean up context
UIGraphicsEndImageContext();
[self setBackgroundImage:overlaidImage forState:state];
}
Are you being too miserly with your original image, and forcing it to stretch rather than shrink? I've found best results out of images that fit the same aspect ratio and were reduced in size. Might not solve your problem tho.