I have a couple of questions.
I have a loaded UIImage and i would like to:
1st - draw another image onto my loaded UIImage
2nd - draw a line (with color and thickness) onto my loaded UIImage
I would greatly appreciate if you would come up with some basic stuff, i'm still a noob :)
There's another alternative and it comes using core-graphics.
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
UIImage *bottomImage = ...;
CGRect bottomImageRect = ...;
CGContextScaleCTM(context, 1.0, -1.0);
CGContextTranslateCTM(context, 0, -bottomImageRect.size.height);
CGContextDrawImage(context, bottomImageRect, bottomImage.CGImage);
CGContextRestoreGState(context);
CGContextSaveGState(context);
UIImage *topImage = ...;
CGRect topImageRect = ...;
CGContextScaleCTM(context, 1.0, -1.0);
CGContextTranslateCTM(context, 0, -topImageRect.size.height);
CGContextDrawImage(context, topImageRect, topImage.CGImage);
CGContextRestoreGState(context);
CGPoint origin = ...;
CGPoint end = ...;
CGContextMoveToPoint(context, origin.x, origin.y);
CGContextAddLineToPoint(context, end.x, end.y);
CGContextSetStrokeColorWithColor(context, [UIColor whatever].CGColor);
CGContextStrokePath(context);
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
EDIT:
Changed the code a little so that images are not inverted
Related
I need to take a UIImage and to add a semi-transparent layer in order to produce a new UIImage. I think I'm getting close but something is still wrong. Here's my code:
- (UIImage*) addLayerTo:(UIImage*)source
{
CGSize size = [source size];
UIGraphicsBeginImageContext(size);
CGRect rect = CGRectMake(0, 0, size.width, size.height);
[source drawInRect:rect blendMode:kCGBlendModeNormal alpha:0.18];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 0.2, 0.5, 0.1, 0.18);
CGContextFillRect(context, rect);
UIImage *testImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return testImg;
}
You forgot to draw the current image you want to blend with source image in current context.
- (UIImage*) addLayerTo:(UIImage*)source
{
CGSize size = [source size];
UIGraphicsBeginImageContext(size, NO, [UIScreen mainScreen].scale); // Use this image context initialiser instead
CGRect rect = CGRectMake(0, 0, size.width, size.height);
[self drawInRect: rect] // Draw the current image in context
[source drawInRect:rect blendMode:kCGBlendModeNormal alpha:0.18]; // Blend with other image
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 0.2, 0.5, 0.1, 0.18);
CGContextFillRect(context, rect);
UIImage *testImg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return testImg;
}
- (UIImage*) addLayerTo:(UIImage*)source
{
CGSize size = [source size];
// create context with UIScrean scale
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
// get new context
CGContextRef ctx1 = UIGraphicsGetCurrentContext();
// draw view
CGContextDrawImage(ctx1, CGRectMake(0.0f, 0.0f, size.width, size.height), source.CGImage);
// set fill color
UIColor *fillColor = [UIColor purpleColor];
// fill with it
CGContextSetFillColorWithColor(ctx1, fillColor.CGColor);
CGContextFillRect(ctx1, CGRectMake(0, 0, size.width, size.height));
// create new image
UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
// end context
UIGraphicsEndImageContext();
return outputImage;
}
Hi in my iOS application I want to rotate the UIImage data in 90 Degrees.
I used the below code for 180 degree rotation - and it works fine.
- (UIImage*)upsideDownBunny:(UIImage *)img {
CGSize imgSize = [img size];
UIGraphicsBeginImageContext(imgSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextRotateCTM(context, M_PI);
CGContextTranslateCTM(context, -imgSize.width, -imgSize.height);
[img drawInRect:CGRectMake(0, 0, imgSize.width, imgSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
But when I try to rotate in 90 degree it is not working - please correct me
- (UIImage *)upsideDownBunny:(UIImage *)img {
CGSize imgSize = [img size];
UIGraphicsBeginImageContext(imgSize);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextRotateCTM(context, M_PI_2);
CGContextTranslateCTM(context, -imgSize.width, -imgSize.height);
[img drawInRect:CGRectMake(0, 0, imgSize.width, imgSize.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
Try this...
UIImage * LandscapeImage = [UIImage imageNamed: imgname];
UIImage * PortraitImage = [[UIImage alloc] initWithCGImage: LandscapeImage.CGImage
scale: 1.0
orientation: UIImageOrientationLeft];
hope this helps you!
Try this
- (UIImage *)upsideDownBunny:(UIImage *)image {
// Rotate in degrees
CGFloat degrees = M_PI_2;
// Calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0, 0, image.size.width, image.size.height)];
CGAffineTransform transform = CGAffineTransformMakeRotation(degrees);
rotatedViewBox.transform = transform;
CGSize rotatedSize = rotatedViewBox.frame.size;
// Create image context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef context = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image.
CGContextTranslateCTM(context, rotatedSize.width * 0.5f, rotatedSize.height * 0.5f);
// Rotate the image context
CGContextRotateCTM(context, degrees);
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(-image.size.width * 0.5f, -image.size.height * 0.5f, image.size.width, image.size.height), [image CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
The problem is your context is being rotated around (0,0) which is the top left corner and after 90 degrees rotate it will go out of bounds. So you need to move the origin of the context to middle.
In the code below I'm adding a small image to a large image. I need to be able to apply a transform to the small image. Right now something weird is going on, for example if I pass in a transform of CGAffineTransformMakeRotation(M_PI_2), the newImage is not rotated in place but rather drawn somewhere off screen. How can I fix this?
+ (UIImage*)addToImage:(UIImage *)baseImage newImage:(UIImage*)newImage atPoint:(CGPoint)point transform:(CGAffineTransform)transform {
UIGraphicsBeginImageContextWithOptions(baseImage.size, NO, 1);
CGContextRef context = UIGraphicsGetCurrentContext();
[baseImage drawInRect:CGRectMake(0, 0, baseImage.size.width, baseImage.size.height)];
CGRect newRect = CGRectMake(point.x,
point.y,
newImage.size.width,
newImage.size.height);
CGContextConcatCTM(context, transform);
[newImage drawInRect:newRect];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
Note that I only want to apply the transform to newImage, not baseImage.
Seems like you just forgot to translate the origin of the context before and after the rotation. Here, try this:
- (UIImage*)addToImage:(UIImage *)baseImage newImage:(UIImage*)newImage atPoint:(CGPoint)point transform:(CGAffineTransform)transform {
UIGraphicsBeginImageContextWithOptions(baseImage.size, NO, [[UIScreen mainScreen] scale]);
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect baseRect = CGRectMake(0, 0, baseImage.size.width, baseImage.size.height);
[baseImage drawInRect:baseRect];
CGRect newRect = CGRectMake(point.x, point.y, newImage.size.width, newImage.size.height);
CGContextTranslateCTM(context, point.x, point.y);
CGContextConcatCTM(context, transform);
CGContextTranslateCTM(context, -point.x, -point.y);
[newImage drawInRect:newRect];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
EDIT:
If you want to rotate the image around its center, add the halves of the image's sides to the corresponding translation values:
float xTranslation = point.x+newRect.size.width/2;
float yTranslation = point.y+newRect.size.height/2;
CGContextTranslateCTM(context, xTranslation, yTranslation);
CGContextConcatCTM(context, transform);
CGContextTranslateCTM(context, -xTranslation, -yTranslation);
I have an overlay of route to be placed over a map. I have to adjust its rotation so that it overlaps exactly with the underlying map view. How can I achieve this? I have found the angle to rotate. How can I rotate my overlay view? Far till now I have added the overlay but can't rotate using transforms. What I noticed is that when I change the angle, the image is not rotating, instead it slides along x axis(side ways).
Here is the code that I tried
- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context
{
NSString *imagePath = [[NSBundle mainBundle] pathForResource:#"routeImage" ofType:#"png"];
UIImage *image = [[UIImage alloc] initWithContentsOfFile:imagePath];
MKMapRect theMapRect = self.overlay.boundingMapRect;
CGRect theRect = [self rectForMapRect:theMapRect];
CGAffineTransform transform = CGAffineTransformMakeRotation((-35.88) / 180.0 * M_PI);
[self setTransform:transform];
CGContextSaveGState(context);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextTranslateCTM(context, 0.0, -theRect.size.height);
CGContextDrawImage(context, theRect,image.CGImage);
CGContextRestoreGState(context);
}
This is what I get
I have a workaround in which I manually rotate the image using GIMP and place it. But I need it to be customized.
This is the image transformed using GIMP and when placed on map as overlay
and this is when I rotate Context using transform [note: while rotating the context the image is rotated but is not at the exact location See image. Also the image breaks on zooming]
This is what I did
//Hayl-Road-Final.png is the actual image without transformation using GIMP
UIImage *image = [[UIImage imageNamed:#"Hayl-Road-Final.png"] retain];
CGImageRef imageReference = image.CGImage;
MKMapRect theMapRect = [self.overlay boundingMapRect];
CGRect theRect = [self rectForMapRect:theMapRect];
// We need to flip and reposition the image here
CGContextScaleCTM(ctx, 1.0, -1.0);
CGContextTranslateCTM(ctx, 0.0, -theRect.size.height);
CGContextRotateCTM(ctx,-35.88);
//drawing the image to the context
CGContextDrawImage(ctx, theRect, imageReference);
Try adding this method:
- (UIImage *) rotate: (UIImage *) image angle:(double)
{
//double angle = 20;
CGSize s = {image.size.width, image.size.height};
UIGraphicsBeginImageContext(s);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(ctx, 0,image.size.height);
CGContextScaleCTM(ctx, 1.0, -1.0);
CGContextRotateCTM(ctx, 2*M_PI*angle/360);
CGContextDrawImage(ctx,CGRectMake(0,0,image.size.width, image.size.height),image.CGImage);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
From your code, you change order of two line. It will be ok:
CGContextScaleCTM(ctx, 1.0, -1.0);
CGContextRotateCTM(ctx,-35.88);
CGContextTranslateCTM(ctx, 0.0, -theRect.size.height);
CGContextDrawImage(ctx, theRect, imageReference);
It is correct with me, please try
I want to crop a part of an uiimageview that on my view controller. I'm creating a rectangle on top of it:
UIGraphicsBeginImageContext(self.view.bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextMoveToPoint(context, newPoint1.x, newPoint1.y);
CGContextAddLineToPoint(context, newPoint1.x, newPoint2.y);
CGContextAddLineToPoint(context, newPoint2.x, newPoint2.y);
CGContextAddLineToPoint(context, newPoint2.x, newPoint1.y);
CGContextAddLineToPoint(context, newPoint1.x, newPoint1.y);
CGContextClosePath(context);
UIColor *blue = [UIColor colorWithRed: (0.0/255.0 ) green: (0.0/255.0) blue: (255.0/255.0) alpha:0.4];
CGContextSetFillColorWithColor(context, blue.CGColor);
CGContextDrawPath(context, kCGPathFillStroke);
I can't figure out how to crop it right. I'm able to retrieve a capture of the screen : entirely blank with my rectangle on it:
UIImage *cropImage = UIGraphicsGetImageFromCurrentImageContext();
rectImage = cropImage;
UIGraphicsEndImageContext();
UIImageCrop *rectImageView = [[UIImageCrop alloc]initWithImage:rectImage];
[self.view addSubview:rectImageView];
So I'm aware that there is something I've missed about it, any help?
- (UIImage *)captureScreenInRect:(CGRect)captureFrame
{
CALayer *layer;
layer = self.view.layer;
UIGraphicsBeginImageContext(self.view.frame.size);
CGContextClipToRect (UIGraphicsGetCurrentContext(),captureFrame);
[layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *screenImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return screenImage;
}
this is just for reference change this code according to your requirement
hope this will help you
You can get cropped image using :
- (UIImage*) getCroppedImage {
CGRect rect = PASS_YOUR_RECT;
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
// translated rectangle for drawing sub image
CGRect drawRect = CGRectMake(-rect.origin.x, -rect.origin.y, your_image.size.width, your_image.size.height);
// clip to the bounds of the image context
// not strictly necessary as it will get clipped anyway?
CGContextClipToRect(context, CGRectMake(0, 0, rect.size.width, rect.size.height));
// draw image
[your_image drawInRect:drawRect];
// grab image
UIImage* croppedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return croppedImage;
}
Hope it helps you.