Im trying to implement a crop feature for my app like the one Instagram has.
Example: http://i.imgur.com/Dq12OAx.png
I need to create an UIView in the form of a rectangle with a square "hole" in the middle.
I have no idea where to start so all help is appreciated.
Its pretty easy. Just subclass UIView, and override drawrect.
- (void)drawRect:(CGRect)rect {
//draw the non-transparent view here, or fill the whole view like
[[UIColor blackColor] setFill];
UIRectFill( rect);
//define the position and size of the "hole"
CGRect yourHole = CGRectMake(left, top, width, height);
//fill that section with clear color
[[UIColor clearColor] setFill];
UIRectFill( yourHole );
}
Related
This is what I want to do:
Take the camera image an put it in a small (not full screen) UIImageView.
Manipulate the image in realtime (e.g. give half of it a red tint).
I have checked around this subject and uncertain as to the best approach. People are recommending both UIImagePickerController and AVCamCaptureManager, or is there something else.
Could I have your advice?
(void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColor(context, CGColorGetComponents([UIColor colorWithRed:0.5 green:0.5 blue:0 alpha:1].CGColor)); // don't make color too saturated
CGContextFillRect(context, rect); // draw base
[[UIImage imageNamed:#"someImage.png"] drawInRect: rect blendMode:kCGBlendModeOverlay alpha:1.0]; // draw image
}
In the rect variable pass the area of the image you would like to tint
I have two rectangles (two closed sub cgpaths).
Rectangle B is small and is present inside Rectangle A. All edges within it.
Is there a direct way to fill color area external to the rectangle B.
CAShapeLayer fillExternalColor something like that? If not a direct way, how to do this programmatically?
A - Purple color
B - Yellow color
So I tried drawing A and then drawing B. I wanted B to be of clear color (for now I put Yellow) but then I see purple color of A..
I found CGRectIntersection method that gives AnB and CGRectUnion method that gives AuB.
Is there a method that gives the rest of the area which is AuB - AnB?
You are using a CAShapeLayer. If your fillColor and your strokeColor are both opaque (alpha 1.0), you can simply set the layer's backgroundColor to fill those pixels that are within the layer's bounds but outside of its stroked and filled path.
My test code:
#implementation ViewController {
CAShapeLayer *layer;
}
- (void)viewDidLoad {
[super viewDidLoad];
layer = [CAShapeLayer layer];
layer.path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(50, 50, 250, 250)].CGPath;
layer.fillColor = [UIColor yellowColor].CGColor;
layer.strokeColor = [UIColor whiteColor].CGColor;
layer.lineWidth = 4;
layer.backgroundColor = [UIColor purpleColor].CGColor;
[self.view.layer addSublayer:layer];
}
- (void)viewDidLayoutSubviews {
layer.frame = self.view.bounds;
}
#end
Result:
I wanted to add red border inner rectangle on UIImage with masked outer part.
I came through this page. The following code is using CGContextEOFillPath can be helpful to others like me. (Some of the code is gathered from other pages.)
-(UIImage ) imageByDrawingBorderRectOnImage:(UIImage )image theRect:(CGRect)theRect
{
// begin a graphics context of sufficient size
UIGraphicsBeginImageContext(image.size);
// draw original image into the context
[image drawAtPoint:CGPointZero];
// get the context for CoreGraphics
CGContextRef ctx = UIGraphicsGetCurrentContext();
// set stroking color and to draw rect
[[UIColor redColor] setStroke];
// drawing with a red stroke color
CGContextSetRGBStrokeColor(ctx, 1.0, 0.0, 0.0, 1.0);
// the line width to 3
CGContextSetLineWidth(ctx, 3.0);
// Add Stroke Rectangle,
CGContextStrokeRect(ctx, theRect);
// Now draw fill outside part with partial alpha gray color
// drawing with a gray stroke color
CGMutablePathRef aPath = CGPathCreateMutable();
// outer rectangle
CGRect rectangle = CGRectMake( 0, 0, image.size.width, image.size.height);
CGPathAddRect(aPath, nil, rectangle);
// innter rectangle
CGPathAddRect(aPath, nil, theRect);
// set gray transparent color
CGContextSetFillColorWithColor(ctx, [UIColor colorWithRed:0.75 green:0.75 blue:0.75 alpha:0.5].CGColor);
// add the path to Context
CGContextAddPath(ctx, aPath);
// This method uses Even-Odd Method to draw in outer rectangle
CGContextEOFillPath(ctx);
// make image out of bitmap context
UIImage *retImage = UIGraphicsGetImageFromCurrentImageContext();
// free the context
UIGraphicsEndImageContext();
return retImage;
}
Regards.
Assuming A is the bigger shape, B is the smaller, inner shape, and bounds refers to the containing rect of A (probably the bounds of the view)
Clip shape B to the context (-addClip should do it)
CGContextClearRect the bounds
Fill shape A
Edit, found the source of this code
Given HoleView : UIView you must set:
self.opaque = NO;
self.backgroudColor = [UIColor clearColor];
and in drawRect:
[[UIColor purpleColor] setFill];
UIRectFill(A);
CGRect gapRectIntersection = CGRectIntersection(B, A);
[[UIColor clearColor] setFill];
UIRectFill(gapRectIntersection);
kCAFillRuleEvenOdd
Specifies the even-odd winding rule. Count the total number of path crossings. If the number of crossings is even, the point is outside the path. If the number of crossings is odd, the point is inside the path and the region containing it should be filled.
Available in OS X v10.6 and later.
Declared in CAShapeLayer.h.
Refer to :CAShapeLayer Class reference
simply I am beginner in developing on ipad and I need to draw rectangle at point x,y with width and height when i clicked or touched button .
I searched on google but i didn't find anything working in button handler
Create rectangleButton in viewDidLoad method and write -(void)rectangleButtonSelected method in your ViewController.m. And also create class RectangleView of UIView.
-(void)rectangleButtonSelected{
RectangleView *temp = [[RectangleView alloc] initWithFrame:CGRectMake(0, 0, 60, 40)];
temp.center = CGPointMake(arc4random()%100, arc4random()%200);
NSLog(#"The Main center Point : %f %f",temp.center.x,temp.center.y);
[self.view addSubview:temp];
}
Implement - (void)drawRect:(CGRect)rect method in RectanglerView.m
- (void)drawRect:(CGRect)rect
{
// Drawing code
context =UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
// And draw with a blue fill color
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1.0);
// Draw them with a 2.0 stroke width so they are a bit more visible.
CGContextSetLineWidth(context, 2.0);
CGContextAddRect(context, self.bounds);
CGContextStrokePath(context);
// Close the path
CGContextClosePath(context);
// Fill & stroke the path
CGContextDrawPath(context, kCGPathFillStroke);
}
I hope it will be helpful to you
You actually need to do this with state. There's only one place you're allowed to do drawing, and that's in drawRect:. So, when the user clicks the button, you need to set some instance variable, like _isShowingRectangle or something, then call setNeedsDisplay on your custom UIView where you're doing your drawing.
Then, in your custom view's drawRect:, you can check if that state variable is set, and draw (or not draw) the rectangle. The code for drawing depends on which graphics layer you're using, but it's probably going to be something like
CGContextRef ctxt = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(ctxt,[[UIColor blackColor] CGColor]);
CGContextSetLineWidth(ctxt,3.0);
CGContextStrokeRect(ctxt,CGRectMake(10,20,100,50));
The above is a UITableViewCell containing two UILabels. The cell has a transparent background using [UIColor clearColor] and the background pattern (you may need to look closely to see it) is set on the UITableView using UIColor's initWithPatternImage.
What I'd like to be able to do is blend the text with the background pattern so that the text has the texture coming through. The only thing is I'm not sure of is the best way of achieving this.
I know I can use NSString instead of UILabels and draw the text directly into an image, but can this then be blended with the background even though it's not being drawn in the same drawRect (i.e. the text image would be drawn in a subclass of UITableViewCell where as the background is being drawn by the UITableView instance)?
The other way is to create an image mask from the text, have another image which is already textured (with the top half white and the bottom half dark grey) and then use that to draw the text, as outlined in this Cocoa with Love tutorial.
Whilst I can obviously use the tutorial to achieve the second implementation, I'm more inclined to explore the first as it'd use no external images and may be more efficient.
Your thoughts, links and code examples will be greatly appreciated.
Please Note: Setting a low alpha value on the UILabels does not achieve the desired effect
If you set the labels as non opaque and an alpha value less than 1.0 it should work. These can be set in either Interface Builder or as code like this:
[theIncidentLabel setOpaque:NO];
[theIncidentLabel setAlpha:0.5];
You can even just set the text color to a color with an alpha value less than 1.0.
[theIncidentLabel setTextColor:[UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.5]];
Using these settings I do see the background texture through labels in a project I'm working on. In my project the list UITableView is also transparent, and the background texture comes from an image loaded in a UIImageView behind the UITableView.
This is simple alpha blending. We figured out through a discussion in comments that this is inadequate for your needs. Instead you can use the alpha masking as explained in the tutorial mentioned.
Alternatively, you could forgo alpha masks and just draw the text to a CGImage, then draw that image on your background pattern with a different blend mode, maybe kCGBlendModeScreen. Here's the drawRect method from the above mentioned tutorial rewritten with this technique:
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
// Draw a black background
[[UIColor blackColor] setFill];
CGContextFillRect(context, rect);
// Draw the text upside-down
CGContextSaveGState(context);
CGContextTranslateCTM(context, 0, rect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
[[UIColor lightGrayColor] setFill];
[text drawInRect:rect withFont:[UIFont fontWithName:#"HelveticaNeue-Bold" size:40.0]];
// Draw it again in a darker color.
[[UIColor darkGrayColor] setFill];
CGContextTranslateCTM(context, 0, 50.0);
[text drawInRect:rect withFont:[UIFont fontWithName:#"HelveticaNeue-Bold" size:40.0]];
CGContextRestoreGState(context);
// Create an text image from what we've drawn so far
CGImageRef textImage = CGBitmapContextCreateImage(context);
// Draw a white background (overwriting the previous work)
[[UIColor whiteColor] setFill];
CGContextFillRect(context, rect);
// Draw the background image
CGContextSaveGState(context);
[[UIImage imageNamed:#"shuttle.jpg"] drawInRect:rect];
// Set the blend mode. Try different options to meet your tastes.
CGContextSetBlendMode(context, kCGBlendModeScreen);
// Draw the text.
CGContextDrawImage(context, rect, textImage);
// Clean up.
CGContextRestoreGState(context);
CGImageRelease(textImage);
}
I have a UIScrollView that contains a subview that I want to fill with a texture.
- (void)drawRect:(CGRect)rect {
CGImageRef image_to_tile_ret_ref = CGImageRetain(wood.CGImage);
CGRect tile_rect;
tile_rect.size = wood.size;
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextBeginPath(context);
CGContextMoveToPoint(context, 0, 0);
CGContextDrawTiledImage(context, tile_rect, image_to_tile_ret_ref);
// Something here to make it fill a big area
CGContextFillPath(context);
CGImageRelease(image_to_tile_ret_ref);
}
This just seems to fill the visible area of the scroll view and when I scroll, the rest is white. How do I draw a rectangle beyond the bounds of the rect? Is that bad?
If you want to draw a background color in this is too much. UIScrollView can have a background color. That color can be created from a patter that is an image.
You can create a pattern color
UIColor * bgColor = [UIColor colorWithPatternImage:[UIImage imageNamed:#"imgname.png"]];
scrollView.backgroundColor = bgColor;