I'm working in a function for scaling and crop image (similar to camara app) for iOS, the code below works fine, just that the resulting image came up side down, and I would like to understand why.
Thanks
- (UIImage*)imageByCropping:(UIImageView *)imageViewToCrop toRect:(CGRect)rect
{
//create a context to do our clipping in
CGRect newRect = CGRectApplyAffineTransform(rect, imageViewToCrop.transform);
UIImage *imageToCrop = imageViewToCrop.image;
UIGraphicsBeginImageContext(newRect.size);
CGContextRef currentContext = UIGraphicsGetCurrentContext();
//create a rect with the size we want to crop the image to
//the X and Y here are zero so we start at the beginning of our
//newly created context
CGRect clippedRect = CGRectMake(0, 0, rect.size.width, rect.size.height);
CGContextClipToRect( currentContext, clippedRect);
//draw the image to our clipped context using our offset rect
CGContextDrawImage(currentContext, newRect, imageToCrop.CGImage);
//pull the image from our cropped context
UIImage *cropped = UIGraphicsGetImageFromCurrentImageContext();
//pop the context to get back to the default
UIGraphicsEndImageContext();
return cropped;
}
I've also came across this issue without explanation. But have found a workaround that solves that problem. Just put the following two lines in your code and try it again. It works for me.
CGContextTranslateCTM(context, 0.0, newRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);//flip context
Related
i am trying to merge two different images in single image and trying to save it in the photo gallery. But the sticker which i am trying to merge on the image is getting stretched and not properly align to x and y in the image.
the code i am using is as below:
- (UIImage*)buildImage:(UIImage*)image
{
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
[image drawAtPoint:CGPointZero];
CGFloat scale = image.size.width / _workingView.width;
NSLog(#"%f",scale);
CGContextScaleCTM(UIGraphicsGetCurrentContext(), scale, scale);
[_workingView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *tmp = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return tmp;
}
here in this code _workingview is the view containing the sticker image inside it & image in the arguement is the main image which we are passing in the function
i would be very much thank full for your help
Thanks Guys
CGFloat width, height;
CGFloat width, height;
UIImage *inputImage; // input image to be composited over new image as example
// create a new bitmap image context at the device resolution (retina/non-retina)
UIGraphicsBeginImageContextWithOptions(CGSizeMake(width, height), YES, 0.0);
// get context
CGContextRef context = UIGraphicsGetCurrentContext();
// push context to make it current
// (need to do this manually because we are not drawing in a UIView)
UIGraphicsPushContext(context);
// drawing code comes here- look at CGContext reference
// for available operations
// this example draws the inputImage into the context
[inputImage drawInRect:CGRectMake(0, 0, width, height)];
[stickerImage drawInRect:CGRectMake(yourX,yourY,othertWidth,otherHeight)]
// pop context
UIGraphicsPopContext();
// get a UIImage from the image context- enjoy!!!
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
// clean up drawing environment
UIGraphicsEndImageContext();
I have a problem to rotate UIImage without quality loss. Now I am using ready method provided by BFKit imageRotatedByDegrees:, but my image become diffused (blurred).
Sample code:
UIImage *image = [[UIImage imageNamed:#"car"] imageRotatedByDegrees:(((float)arc4random() / ARC4RANDOM_MAX) * (360))];
Code of imageRotatedByDegrees: :
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees
{
// calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);
// // Rotate the image context
CGContextRotateCTM(bitmap, DegreesToRadians(degrees));
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Is there another way to rotate UIImage without quality loss?
I'm the author of BFKit, and when I read about your question I investigated about that issue.
In the latest version (1.6.4) I've fixed that!
Now the image will no more be diffused (blurred).
My aim was to rotate an image that was in my MKAnnotationView. So I solved the problem by rotating not image, but whole MKAnnotationView.
An answer which helped me is this.
My code in MKMapViewDelegate method mapView:viewForAnnotation::
annotationView.transform = CGAffineTransformMakeRotation((((float)arc4random() / ARC4RANDOM_MAX) * (360)));
I am having problem understanding the reason for the following method, to return images that are visibly pixelated. I have double checked the size of the image, and it is fine. What's more, without tinting it, the image edges are smooth, and lack pixelation.
The method for tinting image, based on IOS7 ImageView's tintColor property, works fine, however I would love to find out what is wrong with the following code, because it seems to work for everybody but me. Thanks!
- (UIImage *)imageTintedWithColor:(UIColor *)color
{
if (color) {
UIImage *img = self; // The method is a part of UIImage category, hence the "self"
UIGraphicsBeginImageContext(img.size);
// get a reference to that context we created
CGContextRef context = UIGraphicsGetCurrentContext();
// set the fill color
[color setFill];
// translate/flip the graphics context (for transforming from CG* coords to UI* coords
CGContextTranslateCTM(context, 0, img.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// set the blend mode to color burn, and the original image
CGContextSetBlendMode(context, kCGBlendModeColorBurn);
CGRect rect = CGRectMake(0, 0, img.size.width, img.size.height);
CGContextDrawImage(context, rect, img.CGImage);
// set a mask that matches the shape of the image, then draw (color burn) a colored rectangle
CGContextSetBlendMode(context, kCGBlendModeSourceIn);
CGContextAddRect(context, rect);
CGContextDrawPath(context,kCGPathFill);
// generate a new UIImage from the graphics context we drew onto
UIImage *coloredImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
//return the color-burned image
return coloredImg;
}
return self;
}
Change this line:
UIGraphicsBeginImageContext(img.size);
to:
UIGraphicsBeginImageContextWithOptions(img.size, NO, 0);
If your images will never have an transparency, change the NO to YES.
I'm drawing a circle image using core graphics with a modified implementation of this SO answer
Here's my source:
+ (UIImage*)circularImageWithRadius:(CGFloat)radius color:(UIColor*)color{
CGRect rect = CGRectMake(0.0f, 0.0f, radius*2, radius*2);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, color.CGColor);
CGContextFillEllipseInRect(context, rect);
UIImage* image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
The edges are blurry and I'm not sure why (I thought it didn't matter what resolution the device was, it would work right out of the box).
I tried replacing CGContextFillEllipseInRect(context, rect); with CGContextFillRect(context, rect); and that was blurry too. Then I tried CGContextFillRect(context, CGRectMake(0, 0, radius*4, radius*4) and it works perfectly, sharp image and everything (albeit being a a square, not a circle). So I changed back to CGContextDrawEllipseInRect(context, CGRectMake(0, 0, radius*4, radius*4) but this was my result:
whereas with the rectangle, it was the same size as when using radius*2 but with a much sharper image.
How can I fix my blurry issue and why does CGContextFillEllipseInRect not fill the pre-defined image rect?
I feel dumb for having found this immediately after I posted but this answer pointed the way.
I just added
if(UIGraphicsBeginImageContextWithOptions != NULL) {
UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0.0);
} else {
UIGraphicsBeginImageContext(rect.size);
}
instead of just UIGraphicsBeginImageContext(rect.size); into my original source and it's crystal clear and sharp.
For Swift 3.0
UIGraphicsBeginImageContextWithOptions(rect.size, false, 0.0)
defer { UIGraphicsEndImageContext() }
if let context = UIGraphicsGetCurrentContext() {
/// Do Stuff
}
I have a UIImage which is an image of a mountainous landscape. I need to show locations on this image, by turning corresponding 2-3 pixels at the spot to red. How do I accomplish this? Thanks!
You can draw image to graphics context like this:
CGRect imageRect = CGRectMake(0, 0, width, height);
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
//Save current status of graphics context
CGContextSaveGState(context);
CGContextDrawImage(context, imageRect, image.CGImage);
And then just draw a point on it wherever you want like this:
//CGContextFillRect(context, CGRectMake(x,y,1,1));
//Fix error according to #gsempe's comment
CGContextFillRect(context, CGRectMake(x,y,1./(image.scale),1./(image.scale)))
Then just save it to UIImage again:
CGContextRestoreGState(context);
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
You also should take care of image's orientation. Here is some good article on it.