i have to animate text around a circle. The text will also scale up/down. Whats the best approach to accomplish this? (i am using Quartz 2D)
My approach is:
-- Calculate point using sin and cos methods.
-- Move Pen there and draw text with alpha and size.
-- Clear the screen
-- Calculate next point using sin and cos methods.
-- Move pen there and draw text with alpha and size.
-- clear the screen
so on...
any better way?
If you're targeting iPhone OS ≥3.2, use CATextLayer.
Otherwise, you could create a UILabel and modify its transformation value, or control a CALayer directly.
If you're constrained to Core Graphics the method your described is the best already, but CG is not an animation framework. You should use Core Animations for UI animations.
Related
I'm writing an app that could make good use of the Apple Watch's fitness tracker design, here:
So far, I've created the basic outline which is just a CAShapeLayer with a CGPath of an ellipse. I use strokeStart and strokeEnd to animate the progress. My problem comes when applying a gradient to the outline. How do I apply a gradient like above to the stroke of a CGPath?
The cleanest way to do this without having to drop down to Core Graphics or GL is to create a layer containing the angle gradient that you want the ring filled with, mask it with a CAShapeLayer containing your circular path (with the appropriate line width and cap settings), then, as you’re currently doing, use the shape layer’s strokeEnd property to set the “fill” percentage. Note that there isn’t a built-in way to create an angle gradient—you can use one of the suggestions in this answer for that.
edit: Also, you’ll need a pair of semicircular “cap” images, one at each end of the ring—as the fill percentage gets close to 100%, the region at the top will reveal the discontinuity between the start and end color. In your example image above, you’d need a red semicircle oriented like this ( at the start, and a pink one oriented like this ) with a translation/rotation transform tracking the end.
additional edit: Also also, since the end-cap semicircle will be moving along the gradient, you’ll need it to change color, interpolating from the start color to the end color as the fill amount goes from 0% to 100%. Best way to do that is with a shape layer with a semicircular path, since you can set the fillColor of that without having to redraw image contents.
We did this for an iOS app.. but quickly stopped as it gets bogged down quickly.
I think Apple is using images.. as they do in the Lister example
I have been looking for the solution on the web for a long time. Most tutorials are fairly simple about adding shadow to a UIView. I also noticed that if we add a shadow to an UIImageView. The shadow shape could perfectly fit the shape of the content image if the image itself has alpha channel in it. Say for example, if the image is an animal with transparent background, the shadow shape is also the same as that animal (not a rectangle shadow as same as UIImageView frame).
But these are not enough. What I need to do is to add some changes to the shadow so it may have some rotation angle and compressed (squeezed or shift) effect so that looks like the sunlight comes from a certain spot.
To demonstrate what I need, I upload 2 images below, which I captured from the Google Map App created by Apple. You can imagine the Annotation Pin is an image which has the Pin shape, so the shadow is also "pin shaped", but it is not simply "offset" with a CGSize, you can see the top of the shadow is shifted right about 35 degrees and slightly squeezed the height.
When we tap and hold and pin, the shadow is also animated away from the pin, so I believe that such shadow can be made programmably.
The best shadow tutorial I can found so far is http://nachbaur.com/blog/fun-shadow-effects-using-custom-calayer-shadowpaths But unfortunately, that cannot make this effect.
If anyone know the answer or know any better words to search for, please let me know. Thank you.
(Please note that the shape of the image is dynamic in the App, so using any tool like Photoshop to pre-render the shadow is not an option.)
In order to create dynamic effects like this, you have to use Core Graphics. It's incredibly powerful once you know how to use it. Basically you need to set a skew transform on the context, set up a shadow and draw the image. You will probably have to use transparency layers as well.
It doesn't sound like you can use CALayer shadows, since that is meant to solve a specific use-case. The approach Apple takes with the pin marks on the map is to have two separate images that are created ahead of time (e.g. in Photoshop) and they position them within the map relative to a reference point.
If you really do need to do this at run-time, it should still be possible by using either Core Graphics or ImageKit. To get a blurred shadow appearance, you can use the kCICategoryBlur CIFilter. You can then convert the image to grayscale. And to get that compressed look you just need to resize and skew the image.
Once you have two separate images, you can either take the CGImageRef for the shadow image and can set that as the content of another sublayer, or you can add it as a separate view.
If you know what all the shapes are, you could just render a shadow image in Photoshop or something.
I'm a novice in OpenGL ES 1.1(for IOS) texturing and I have a problem with making the effect of motion blur. During googling, I found that I should render my scene in different time moments to several textures and then draw all these textures on the screen with different alpha values. But the problem is that I don't know how to implement all this!So,my questions are:
How to draw a 2D texture on the screen? Should I make a square and put my texture on it?Or may be, there is a way to draw a texture on the screen directly?
How to draw several textures(one upon another) on the screen with different alpha values?
I've already come up with some ideas, but I'm not sure if they are correct or not.
Thanks in advance!
Well, of course the first advice is, understand the basics before trying to do advanced stuff. Other than that:
Yes indeed, to draw a full-screen texture you just draw a textured screen-sized quad. An orthographic projection would be a good idea in this case, making the screen-alignment of the quad and its proper sizing easier. For getting the textures in the first place (by rendering into them), FBOs might be of help, but I'm not sure they are supported on ES 1 devices, otherwise the good old glCopyTexSubImage2D will do, too, albeit requiring a copy operation.
Well, you just draw multiple textured quads (see 1) one over the other. You might configure the texture environment to scale the texture's color with the quad's base color (glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE)) and give your quads a color of (1, 1, 1, alpha) (of course lighting should be disabled). Additionally you have to enable alpha blending (glEnable(GL_BLEND)) and use an appropriate blending function (glBlendFunc(GL_SRC_ALPHA, GL_ONE) should do).
But if all these terms don't tell you anything, you should rather first learn the basics using a good learning resource before delving into more advanced effects.
I have a custom UIView (graphView) that draws a complex graphic in the drawRect based on iPad screen size 1024 x 768. I'd like to take this view and shrink it down for use on the iPhone. I'm hoping to use the same drawing code and shrink the view instead of recalculating my graphic or creating a bitmap cache. The view created on the fly with no Interface Builder.
What is the best approach to do the shrinking?
Should I put the view inside of a UIScrollView?
Thanks!
If possible, just change the current transform matrix before drawing, using something like CGContextScaleCTM. That'll scale all your measurements sent into Core Graphics prior to rasterisation.
If that isn't possible for whatever reason, you should consider still drawing at 1024x768 but applying a suitable transform to the UIView using CGAffineTransformMakeScale. That'll draw at the original pixel size then scale down as a raster operation on the output pixels so it'll be less efficient.
I have a CCSprite that was created from a png with transparent background.
I want to be able to apply colors to this sprite in a way that I`m free to define which color it is, without the actual color of the sprite affecting the amount of each color I have to add.
I`ve tried this:
mySprite.color = ccc3(200,200,255);
In an attempt to add a little blue-ish feel to my sprite, but as it works by setting the amount of tint that's gonna be displayed based on existant color of the sprite, and my sprite has virtually no blue in any of it (most of it is yellow) the resulting effect is pretty sketchy, everything gets really dark, and there is one slight blue-ish coloring, but not as I wanted.
The ideal effect for me on this case would be to ADD a light blue mask to it with very low alpha.
Is there an easy way to do that without composing sprites?
I've tried using CCTexture2D, but had no luck, as there is no built in method for working with colors, and most tutorials only teach you how to build textures out of image files.
This is deceptively hard to do in code with the original sprite. Another option would be:
create a new sprite, which is just a white outline version of your original sprite
the color property of this white sprite will now respond exactly to the RGB values you pass in
so pass in your light blue value to the white sprite and set the opacity correctly
then overlay it on your original sprite
Any good?
The only way you can achieve this is by overlaying (masking) the sprite with the proper OpenGL blend functions. When you say "add a light blue mask" then that's what you need to do. You may find this visual blendfunc tool helpful, if only to understand how blending with mask sprites works and what you can achieve with it. There's no built-in support for this by Cocos2D however, so you'll have to revert to pure OpenGL inside a cocos2d node's -(void) draw {} method.
Tinting (changing the color property) will only modify the RGB channels of the entire image by changing the vertex colors of all 4 vertices.