I'm trying to draw a triangle within a rectangle frame. I'm using two hand-gesture points startPoint and endPoint and calculating the thirdPoint (making the triangle equilateral). Drawing the triangle works fine the problem is that the frame that hold the rectangle size is base on the area of the hand-gesture so sometimes the third point gets cut off and does not show see bellow:
Is there any way I can add that third point so the frame so it takes it in consideration and does not get cut off.
Related
I'm animating objects falling onto a board from above, and I want to animate the board 'falling back' as the objects fall upon it. Objects can fall at any point on the board, and when the board 'falls back' I am scaling the board to a smaller scale.
When using CGAffineTransformScale objects scale based on their anchor point, the centre of the object; I want to scale the board and then line up the transformed board with the object that has fallen on it, so that the object that has fallen appears to stay in the same place relative to the board (or, more correctly, the board stays in the same place relative to the position of the board).
I spent hours, and hours changing the anchor point to the position that the object fell, but this revealed a fundamental misunderstanding on my part of how layer.anchorPoint actually works.
I imagine the solution is deriving a vector from the centre of the board to the given falling object and then somehow adjusting position of the board in the transformation so it's the same place. This is where I need help!
As you'd expect in these situations, an animated gif is required.
CALayer's anchorPoint property is the correct property to use for this, with the one minor annoyance that it works in the unit coordinate space, that is, it goes from 0 to 1, not in pixels:
You specify the value for this property using the unit coordinate space. The default value of this property is (0.5, 0.5), which represents the center of the layer’s bounds rectangle. All geometric manipulations to the view occur about the specified point. For example, applying a rotation transform to a layer with the default anchor point causes the layer to rotate around its center. Changing the anchor point to a different location would cause the layer to rotate around that new point.
Because of this, setting an anchor point in pixels would obviously result in some very strange behaviour. You would need to calculate your new anchor point in the unit coordinate space for it to work properly, so, instead of doing something like this:
board.layer.anchorPoint = CGPointMake(ball.x, ball.y);
you would do this:
board.layer.anchorPoint = CGPointMake(ball.x / board.layer.bounds.size.width,
ball.y / board.layer.bounds.size.height);
UPDATE: When you change the anchorPoint property, the view will move, because the anchorPoint, which is set relative to the layer in the unit coordinate space, is anchored to the layer's position property, which is set in the superview's coordinate space. In this way, when you change the value of the anchorPoint property, the view will move such that the point at the new anchor point is at the same place as the old one. You will need to compensate for this, as described in this answer.
Is it possible to change the origin of an NSImage? If so how would I go about doing this. I have coordinates in regular cartesian system some of them with negative values and I am trying to draw them at the corresponding point in the NSImage but since the origin is at (0,0) there are some missing.
EDIT:Say I have an drawing aspect that needs to be done to an image at the point (-10,-10), currently this doesn't show up. Is there a way to fix that?
If it's like in iOS (you may have to adapt a little the code) and if my memory is still good, you have to do this, since origin is readOnly:
CGRect myFrame = yourImage.frame;
myFrame.origin.x=newX; myFrame.origin.y=newY;
yourImage.frame = myFrame;
I think you are confusing an NSImage with it's container. An NSImage has no bounds or frame, and thus no origin. It does have a size which may represent the pixel dimensions of its birtmap representation ( if it has one) or otherwise could represent it's bounding box ( if it is a vector image). Drawing in an image at a pixel location of (-10,-10) doesn't really make sense.
An NSImage is displayed in a container ( typically an NSImageView), and the container's bounds.origin will dictate the placement of the image relative to the imageView, but you can't modify pixels beyond the edge of the bitmap plane.
In any case you probably want to be using a subclassed NSView in which you would override the drawRect method for your custom drawing. NSView does have a bounds.origin but this is not relevant to your in-drawing coordinates, but rather to the position of the drawn content as a whole to the view's bounding box. The coordinate system that you will be drawing into will be referenced to your graphics context which will (usually) pin the origin (0,0) to the bottom left corner (OSX) or top left corner (iOS). If you are trying to represent negative points on a Cartesian plane, you will need to apply a translation transform to map your points into this positive coordinate space.
I'm trying to explain in a few words, badly, something which Apple explains in great detail in their Quartz 2D Programming Guide.
Developing an iPhone game with Cocos2d-iphone. I have a huge sprite and I want to apply a CCLiquid (or any other liquid-wave-like effect) on it.
However, the image is huge, so it consumes a lot of memory (without mentioning I have many other big elements during gameplay).
Well, I figured I could try to "only apply the liquid effect on the area that is visible by the player" (dimensions of such area being 480x320). That could help a lot.
I already got a CGRect representing the area of the CCSprite that should be affected. However, how would I actually apply the effect only within such area? Any ideas?
You could manually create a CCSprite from a sprite frame and set the boundaries of that frame to your CGRect. Then use the effect on this resulting CCSprite. Essentially, your original CCSprite image would act like a larger texture atlas form which you are specifying a small portion of that image to be the actual frame of your sprite. If you layered this new copied sprite on top of your main, larger one in the exact position, it would appear to be part of that larger sprite, but only the small CGRect portion would be affected by your code.
I have a sprite and if it is touched the touch should be recognized. I used the coordinates to do so. I took the coordinates (min x, min y, max x , max y)of the sprite image. But The sprite image is not a rectangular shape. So, even if I touch the coordinates outside the sprite and inside the rectangular bounds the sprite is recognized.
But for my application I need only the sprite to be recognized. So, I have to take only the coordinates of the sprite, but it is not regular shape. I am using CCSprite in my program.
So, what can I do to for only the sprite to be selected ? Which classes should use for this?
Thank You.
You could try one of the following...
Create a bounding box smaller than the absolute extents of the sprite image. Yes it will be smaller than the sprite. This will eliminate the dead space click detection of the sprite the trade off being parts of your sprite which look selectable won't be
Use a circular bounding area to detect if the user has clicked on your sprite. Again you will have the dead space problem in my first suggestion but the sphere may give you some better coverage area over the sprite giving you better results on touch detection
This is a standard problem in physics collision detection systems which often end up using circles or rectangles as their collision bodies. I would go with the either a circle or rectangle smaller than the size of your sprite as your bounding area. Going finer detail than that you could generate bounding area polygons. This would however introduce a whole bunch of new issues and concerns.
I am building a Cocos2D game right now and what I am doing is first I step through my sprites and see which sprites the touch hit (they overlap in my app)
Then, for each sprite hit I use [sprite convertTouchToNodeSpace] to get an X,Y co-ordinate inside the sprite, which I can use (although the Y axis is flipped) to reference the CGImage I created the sprite with.
If the pixel at the touch point is 'clear' ie alpha 0, then the sprite was not really touched, and I check the next sprite in the z-order to see if it has color where it was touched.
Sometimes I think I should be using a two color mask image to go along with each sprite, not the sprite image. But, I am mr. make it work, then make it fast.
I realise this is not super efficient, but I do not have very many sprites and I do this only for touches.
Hello I am having a hard time making this UI element look the way I want (see screenshot). Notice the image on the right--how the line width and darkness looks inconsistent compared to the image on the left (which happens to be a screen grab from safari) where the border width is more consistent. How does apple make their lines so perfect?
I'm using a CALayer and the Core Graphics API to draw the image on the right. Is it possible to draw such perfect lines with the standard apis?
The problem with drawing a 1-pixel path is that Quartz draws paths on an exact point grid, starting from {0,0}. This means that if you stroke a vertical path starting at {10,10} with a 1-point width, half of that line will render in the pixel to the left of the coordinate and half in the pixel to the right, causing a blurring effect.
You should therefore shift your drawing by {0.5,0.5} if you want lines to draw on exact pixels.
You can definitely draw what you want with Quartz.
Apple uses images for the tab elements.