Hi,
I want to rotate my UIImageView without moving the whole "png". No code is only to test what happens
_fanImage.transform = CGAffineTransformMakeRotation(45);
It turns but the whole image moves. What can I do that this doesn't happen ?
You can try something like this.. You should rotate the UIImage rather than UIImageView.
- (UIImage *)imageWithTransform:(CGAffineTransform)transform {
CGRect rect = CGRectMake(0, 0, self.size.height, self.size.width);
CGImageRef imageRef = self.CGImage;
// Build a context that's the same dimensions as the new size
CGContextRef bitmap = CGBitmapContextCreate(NULL,
self.size.width,
self.size.height,
CGImageGetBitsPerComponent(imageRef),
0,
CGImageGetColorSpace(imageRef),
CGImageGetBitmapInfo(imageRef));
// Rotate and/or flip the image if required by its orientation
CGContextConcatCTM(bitmap, transform);
// Draw into the context; this scales the image
CGContextDrawImage(bitmap, rect, imageRef);
// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];
// Clean up
CGContextRelease(bitmap);
CGImageRelease(newImageRef);
return newImage;
}
I think you mean that you want your image view to rotate around it's center point. Is that right? If so, that's what a view should do by default.
You should do a search on "Translating, Scaling, and Rotating Views" in Xcode and read the resulting article.
Note that all of iOS's angles are specified in radians, not degrees.
Your sample images aren't really helpful, since we can't see the frame that the image view is drawn into. It's almost impossible to tell what your image views are doing and what they are supposed to be doing instead based on the pictures you linked from your dropbox.
A full 360 degrees is 2pi.
You should use
CGFloat degrees = 45;
CGFloat radians = degrees/180*M_PI;
_fanImage.transform = CGAffineTransformMakeRotation(radians);
That will fix the rotation amount for your code, but probably not the rotation position.
Related
I have a CGPath shaped like an arrow that I am drawing in the CGContext of my current view. I would like to generate a miniature version (thumbnail) of the arrow to add it as an Image to a UITableView showing all selected arrows.
I am succeeding to downscale a picture of the full context which leaves the arrow smaller than it should be. Ideally I would like to crop the image of the full context to the bounds of the arrow. However, I was not yet successful. Any leads? Thanks for the help!
Here are a picture of the full view containing an arrow and another picture of the thumbnail I am generating.
Ideally the thumbnail above would be cropped to contain the arrow only - not the full context.
The code I use is the follwoing:
- (UIImage*) imageForObject:(id<GraphicalObject>) object
inRect:(CGRect)rect {
UIImage *image = [UIImage new];
CGRect objectBounds = [object objectBounds];
UIGraphicsBeginImageContext(self.view.frame.size);//objectBounds.size);
CGContextRef context =UIGraphicsGetCurrentContext();
[object drawInContext:context];
//doesn't work
CGContextClipToRect(context, objectBounds);
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
The CGRect called objectBounds has two components, an origin and a size. In order the draw the object correctly as a thumbnail, the code needs to scale the image (to get the size right) and translate the image (to move the origin to {0,0}). So the code looks like this
- (UIImage *)getThumbnailOfSize:(CGSize)size forObject:(UIBezierPath *)object
{
// to maintain the aspect ratio, we need to compute the scale
// factors for x and y, and then use the smaller of the two
CGFloat xscale = size.width / object.bounds.size.width;
CGFloat yscale = size.height / object.bounds.size.height;
CGFloat scale = (xscale < yscale) ? xscale : yscale;
// start a graphics context with the thumbnail size
UIGraphicsBeginImageContext( size );
CGContextRef context = UIGraphicsGetCurrentContext();
// here's where we scale and translate to make the image fit
CGContextScaleCTM( context, scale, scale );
CGContextTranslateCTM( context, -object.bounds.origin.x, -object.bounds.origin.y );
// draw the object and get the resulting image
[object stroke];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
I would like to rotate a UIImage from file (a jpeg on the file system) a computed amount of radians, but I would like to rotate it around a point in the image, as well as keep the original size of the image (with transparent gaps in the image where image data no longer exists, as well as cropping image data that has moved outside of the original frame). I would like to then store and display the resulting UIImage. I haven't found any resources for this task, any help would be much appreciated!
The closest thing I have found so far (with some slight modifications) is as follows:
-(UIImage*)rotateImage:(UIImage*)image aroundPoint:(CGPoint)point radians:(float)radians newSize:(CGRect)newSize
{
CGRect imageRect = { point, image.size };
UIGraphicsBeginImageContext(image.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, imageRect.origin.x, imageRect.origin.y);
CGContextRotateCTM(context, radians);
CGContextTranslateCTM(context, -imageRect.origin.x, -imageRect.origin.y);
CGContextDrawImage(context, (CGRect){ CGPointZero, imageRect.size }, [image CGImage]);
UIImage *returnImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return returnImg;
}
Unfortunately, this rotates the image incorrectly (in my tests, somewhere in the neighborhood of 180 degrees more than desired).
to rotate that UIImage image, lets say 90 degrees, you can easily do:
imageView.transform = CGAffineTransformMakeRotation(M_PI/2);
to rotate it multiple times you can use:
UIView animateKeyframesWithDuration method
and to anchor it to some point you can use:
[image.layer setAnchorPoint:CGPointMake(....)];
Many questions are available on SO, but unfortunately I couldn't solve my problem using them.
I've added a overlay view on my camera, and now want to get image within the blue border (only water bottle).
I tried code chunks like following
CGImageRef imageRef = CGImageCreateWithImageInRect([largeImage CGImage], cropRect);
[UIImageView setImage:[UIImage imageWithCGImage:imageRef]];
CGImageRelease(imageRef);
but having two issues
Either cropped image is getting too big
The orientation changes to -90.
for point 1, I think I'm providing cropRect too small thats why it showing very small part of image with too zoomed view. on my other viewController I have UIImageView (where cropped image need to display) of same size as camera rect within blue border.
So question is how to crop the image and what values should I provide for cropRect?
Assuming the image size 1280* 1080 and your crop view size 320*480 You need to do the following
Convert your crop view's frame to Image size rect (0, 0, 1280, 1080) by find the scale factor
float xScale = 1280 / 320;
float yScale = 1080 / 480;
float scaleFactor = (xScale < yScale) ? xScale : yScale;
Multiply cropView frame by scale factor. This will map the screen coordinates to image size coordinates. Then use the new cropRect with the
CGImageCreateWithImageInRect([largeImage CGImage], cropRect);
The problem with different orientation is that CoreGraphics uses a different coordinate system as compare to view's coordinate system. Quartz 2D Coordinate Systems so try setting
[UIImage imageWithCGImage:imageRef].imageOrientation = largeImage.imageOrientation
It looks like I might've potentially found an answer to one of my earlier problems and would be happy to post the solution on SO though I first need to confirm it works properly.
The problem is it seems to be - most of the time, though not always. I've isolated the problematic code - it's a method I created whose purpose is to return a UIImage of what is currently visible on the device's screen. It looks like this:
+ (UIImage *)getImageVisibleOnScreenWith: (CGRect) boundingRect rotationAngle: (CGFloat) angle scalingRatio: (CGFloat) scale entireImageView: (UIImageView *) imageView actualVisibleView: (UIView *) visibleView {
// Create a graphics context the size of the bounding rectangle
UIGraphicsBeginImageContext(boundingRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
// Rotate and translate the context
CGAffineTransform transform = CGAffineTransformIdentity;
transform = CGAffineTransformTranslate(transform, boundingRect.size.width/2, boundingRect.size.height/2);
transform = CGAffineTransformRotate(transform, angle);
transform = CGAffineTransformScale(transform, scale, -scale);
CGContextConcatCTM(context, transform);
// Draw the image into the context
CGContextDrawImage(context, CGRectMake(-imageView.image.size.width/2, -imageView.image.size.height/2, imageView.image.size.width, imageView.image.size.height), imageView.image.CGImage);
// Get an image from the context
UIImage *viewImage = [UIImage imageWithCGImage: CGBitmapContextCreateImage(context)];
// Clean up
UIGraphicsEndImageContext();
// Get the image currently on the screen (it's an intersection of specific UIImageViews)
CGRect visibleImageRect = CGRectIntersection(imageView.frame, visibleView.frame);
UIImage *visibleImage = (__bridge UIImage *)(CGImageCreateWithImageInRect((__bridge CGImageRef)(viewImage), visibleImageRect));
return visibleImage;
}
I pass on the result of this method to another one and noticed it sometimes returns nil - for no apparent reason, well at least I couldn't find any.
As usual, any ideas and help will be appreciated; also let me know if you need to see more code or if there's anything unclear as to what the purpose it is.
Im trying to rotate an image, that i want to draw on a image file (to the context.
Everything works fine, except when i rotate the image.
Basically i have an image; i want to scale and resize the image and then clip it to a rect and finaly draw it to the UICurrentContext;
//create a new graphic context
UIGraphicsBeginImageContext(CGSizeMake(500, 500));
CGContextRef graphicContext = UIGraphicsGetCurrentContext();
CGContextDrawImage(graphicContext, CGRectMake(0, 0, rect.size.width, rect.size.height), image.CGImage);
CGContextRotateCTM(graphicContext, 45 * M_PI/180.0);
UIImage* editedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
//draw it to the current context
[editedImage drawAtPoint:CGPointMake(0,0)];
The thing is when i rotate the image, i dont have a clue what the new size of the imagecontext would be. Next to that, the image in the edited image is not rotated..
You need to rotate the context before you draw. I know this seems silly, but to use the analogy of a piece of paper...this is a piece of paper that cannot move. Instead you must move yourself around it and then draw.
This way, your size will never change because anything too big will just simply be cut off.
EDIT Also, this function takes radians, not degrees, so you don't need to convert as you are doing. If you want 45 degrees it will just be PI / 4 (which is stored as the constant M_PI_4 in math.h).