I want to crop an ellipse from an image in ios. Using core image framework, I know know to crop a reactangular region.
Using core graphics, I am able to clip the elliptical region. But, the size of the cropped image is same as the size of the original image as I am applying mask to area outside the ellipse.
So, the goal is to crop the elliptical region from an image and size of cropped image won't exceed the rectangular bounds of that image.
Any help would be greatly appreciated. Thanks in advance.
You have to create a context in the correct size, try the following code:
- (UIImage *)cropImage:(UIImage *)input inElipse:(CGRect)rect {
CGRect drawArea = CGRectMake(-rect.origin.x, -rect.origin.y, input.size.width, input.size.height);
UIGraphicsBeginImageContext(rect.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextAddEllipseInRect(ctx, CGRectMake(0, 0, rect.size.width, rect.size.height));
CGContextClip(ctx);
[input drawInRect:drawArea];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img;
}
Maybe you have to adjust the drawArea to your needs as i did not test it.
Related
I am trying to resize an image using UIGraphics. The image is one taken with the camera, and I am using this code:
CGSize origImageSize = photograph.size;
//this saves as 140*140 for retina
CGRect newRect = CGRectMake(0, 0, 70, 70);
//scaling ratio
float ratio = MAX(newRect.size.width/origImageSize.width, newRect.size.height/origImageSize.height);
UIGraphicsBeginImageContextWithOptions(newRect.size, NO, 0.0);
CGRect projectRect;
projectRect.size.width= ratio*origImageSize.width;
projectRect.size.height=ratio*origImageSize.height;
//center the image
projectRect.origin.x= ((newRect.size.width-projectRect.size.width)/2);
projectRect.origin.y=((newRect.size.height-projectRect.size.height)/2);
[photograph drawInRect:projectRect];
//get the image from the image context
UIImage *smallImage = UIGraphicsGetImageFromCurrentImageContext();
For some reason the final photo isn't as sharp, it's slightly blurry. Am I doing anything wrong here? Any pointers would be really appreciated. thanks
I assume you calculate rectangle properly. Then make sure you use integral rectangle. Non-integral values may cause sub pixel rendering.
Run your projectRect through CGRectIntegral to get integral rectangle, then use it to render your image.
projectRect = CGRectIntegral(projectRect);
I've been struggling with this method for a while. I am drawing an avatar on top of another image. The user picture I want to be a circle, however I can't seem to figure out how. The user picture is a UIImage and not a UIImageView. I am aware of how to make a circle if it is an imageview. Below is the code. There might be a better approach.
-(UIImage *)drawImage:(UIImage*)pinImage withBadge:(UIImage *)user{
UIGraphicsBeginImageContextWithOptions(pinImage.size, NO, 0.0f);
[pinImage drawInRect:CGRectMake(0, 0, pinImage.size.width, pinImage.size.height)];
[user drawInRect:CGRectMake(20.0, 10.0, user.size.width/2, user.size.height/2)];
UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return resultImage;
}
The result is good, but the user image is still square, it is not circle. I have tried making the add the User image to a UIImageView, transform it to a circle, and then use it in the method by calling yourImageView.image, but no luck. I also tried numerous other ways. My logic is more than likely incorrect.
The desired outcome is a rounded image place on top of a pin/annotation. Where the black dot would be an image (a bigger circle than this).
You can clip the image context to the path of an image
// Start the image context
UIGraphicsBeginImageContextWithOptions(pinImage.size, NO, 0.0);
UIImage *resultImage = nil;
// Get the graphics context
CGContextRef context = UIGraphicsGetCurrentContext();
// Draw the first image
[pinImage drawInRect:CGRectMake(0, 0, pinImage.size.width, pinImage.size.height)];
// Get the frame of the second image
CGRect rect = CGRectMake(20.0, 10.0, user.size.width/2, user.size.height/2)
// Add the path of an ellipse to the context
// If the rect is a square the shape will be a circle
CGContextAddEllipseInRect(context, rect);
// Clip the context to that path
CGContextClip(context);
// Do the second image which will be clipped to that circle
[user drawInRect:rect];
// Get the result
UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
// End the image context
UIGraphicsEndImageContext();
Create a circular path and then clip to that?
CGContextAddArc(ctx, ....);
CGContextClip(ctx);
I have an implementation of AVCaptureSession and my goal is for the user to take a photo and only save the part of the image within the red square border, as shown below:
AVCaptureSession's previewLayer (the camera) spans from (0,0) (top left) to the bottom of my camera controls bar (the bar just above the view that contains the shutter). My navigation bar and controls bar are semi-transparent, so the camera can show through.
I'm using [captureSession setSessionPreset:AVCaptureSessionPresetPhoto]; to ensure that the original image being saved to the camera roll is like Apple's camera.
The user will be able to take the photo in portrait, landscape left and right, so the cropping method must take this into account.
So far, I've tried to crop the original image using this code:
DDLogVerbose(#"%#: Image crop rect: (%f, %f, %f, %f)", THIS_FILE, self.imageCropRect.origin.x, self.imageCropRect.origin.y, self.imageCropRect.size.width, self.imageCropRect.size.height);
// Create new image context (retina safe)
UIGraphicsBeginImageContextWithOptions(CGSizeMake(self.imageCropRect.size.width, self.imageCropRect.size.width), NO, 0.0);
// Create rect for image
CGRect rect = self.imageCropRect;
// Draw the image into the rect
[self.captureManager.stillImage drawInRect:rect];
// Saving the image, ending image context
UIImage *croppedImage = UIGraphicsGetImageFromCurrentImageContext();
However, when I look at the cropped image in the camera roll, it seems that it has just squashed the original image, and not discarded the top and bottom parts of the image like I'd like. It also results in 53 pixels of white space at the top of the "cropped" image, likely because of the y position of my CGRect.
This is my logging output for the CGRect:
Image crop rect: (0.000000, 53.000000, 320.000000, 322.000000)
This also describes the frame of the red bordered view in the superview.
Is there something crucial I'm overlooking?
P.S. The original image size (taken with a camera in portrait mode) is:
Original image size: (2448.000000, 3264.000000)
You can crop images with CGImageCreateWithImageInRect:
CGImageRef imageRef = CGImageCreateWithImageInRect([uncroppedImage CGImage], bounds);
UIImage *croppedImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
Don't forget to add scale parameter otherwise you will get low resolution image
CGImageRef imageRef = CGImageCreateWithImageInRect([uncroppedImage CGImage], CGRectMake(0, 0, 30, 120));
[imageView setImage:[UIImage imageWithCGImage:imageRef scale:[[UIScreen mainScreen] scale] orientation:UIImageOrientationUp]];
CGImageRelease(imageRef);
Swift 3:
let imageRef:CGImage = uncroppedImage.cgImage!.cropping(to: bounds)!
let croppedImage:UIImage = UIImage(cgImage: imageRef)
I have a UIImage that is reading from a transparent PNG (500px by 500px). Somewhere in the image, there is a picture that I want to crop out and save as a separate UIImage. I also want to store the X and Y coordinates based on how many transparent pixels there were on the left and top of the newly cropped rectangle.
I was able to crop an image with this code:
- (UIImage *)cropImage:(UIImage *)image atRect:(CGRect)rect
{
double scale = image.scale;
CGRect scaledRect = CGRectMake(rect.origin.x*scale,rect.origin.y*scale,rect.size.width*scale,rect.size.height*scale);
CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], scaledRect);
UIImage *cropped = [UIImage imageWithCGImage:imageRef scale:scale orientation:image.imageOrientation];
CGImageRelease(imageRef);
return cropped;
}
Which actually cuts off the transparent pixels on the top and left :S (this would be great if I was able to crop the pixels on right and bottom too!). It then resizes the rest of the image to the rectangle I specified. Unfortunately though I need to cut a picture that is in the middle of the image and I need the size to be able to be dynamic.
Been struggling with this for several hours now. Any ideas?
To crop an image, draw it into a smaller graphics context.
For example, let's say you have a 600x600 image. And let's say that you want to crop 200 pixels off all four sides. That leaves a 200x200 rectangle.
So you would make a 200x200 graphics context, using UIGraphicsBeginImageContextWithOptions. Then you would draw the image into it using drawAtPoint:, drawing at the point (-200,-200). If you think about it, you will see that that offset causes just the 200x200 from the middle of the original to be drawn into the actual bounds of the context. Thus you have cropped the image by 200 pixels on all four sides, which is what we wanted to do.
Thus here is a generalized version, assuming that we know the amount to crop from the left, right, top, and bottom:
UIImage* original = [UIImage imageNamed:#"original.png"];
CGSize sz = [original size];
CGFloat cropLeft = ...;
CGFloat cropRight = ...;
CGFloat cropTop = ...;
CGFloat cropBottom = ...;
UIGraphicsBeginImageContextWithOptions(
CGSizeMake(sz.width - cropLeft - cropRight, sz.height - cropTop - cropBottom),
NO, 0);
[original drawAtPoint:CGPointMake(-cropLeft, -cropTop)];
UIImage* cropped = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
After that, cropped is your cropped image.
In the photo albums app there's a build in edit -> cropping tool. Is it possible to use that tool in an app instead of writing it on my own? Is it a part of the framework?
No, there is no built-in crop tool. However, it would not be that hard to write such a tool.
You'd need to create a control that let the user drag around an image in a scroll view, and collect the coordinates.
Then you'd create a graphics context and use the UIImage method drawInRect: to draw the image into a rect that's larger than the graphics context. The result would be to draw a cropped portion of the image into the context. Then you'd extract an image from the graphics context and discard the graphics context.
No that is not part of SDK, but you can easily crop images in iOS.
- (UIImage *)resizeImage:(UIImage *)image width:(float)w height:(float)h {
UIImage *croppedImage = image;
CGSize size = CGSizeMake(w, h);
UIGraphicsBeginImageContext(size);
CGRect rect = CGRectMake(0.0f, 0.0f, size.width, size.height);
[image drawInRect:rect];
croppedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return croppedImage;
}
I created a crop tool that might fit your need. It's not based on a scroll view, but rather letting the user choose a frame around their image.
https://github.com/nicholjs/BFCropInterface