Animating a UIImage or UIImageView?

Question

I\'m trying to animate an image\'s height (from height of 0 pixels to 480 pixels) to create the effect of the image being rendered top-down.

With an UIImageView i notice

Answer 1

You may want to check out Animation Blocks. They're documented quite thoroughly here:

http://developer.apple.com/library/ios/#documentation/WindowsViews/Conceptual/ViewPG_iPhoneOS/AnimatingViews/AnimatingViews.html

All the code there is relevant, because UIImageView is a subclass of UIView.

Happy coding.

Answer 2

You should have a look on Flip Clock for iPad tutorial. It is with core animation, hence has a performance bonus.

Answer 3

As mentioned in the original post, here is the answer i seem to have stumbled upon:

For the top-most imageview, i set the content mode to Top (so it doesnt scale). Then in code, i set the clipsToBounds to True. Now i am able to animate the top-most imageview height thus giving me the effect i am looking for.

Answer 4

Try set your UIImageView's contentMode property to one of the following value. I think what you need is UIViewContentModeScaleAspectFit:

typedef enum {
    UIViewContentModeScaleToFill,
    UIViewContentModeScaleAspectFit,      // contents scaled to fit with fixed aspect. remainder is transparent
    UIViewContentModeScaleAspectFill,     // contents scaled to fill with fixed aspect. some portion of content may be clipped.
    UIViewContentModeRedraw,              // redraw on bounds change (calls -setNeedsDisplay)
    UIViewContentModeCenter,              // contents remain same size. positioned adjusted.
    UIViewContentModeTop,
    UIViewContentModeBottom,
    UIViewContentModeLeft,
    UIViewContentModeRight,
    UIViewContentModeTopLeft,
    UIViewContentModeTopRight,
    UIViewContentModeBottomLeft,
    UIViewContentModeBottomRight,
} UIViewContentMode;

Answer 5

Just a suggestion, assume you have two images: A and X (the X-ray image):

+-------+               +-------+
|       |               |       |
|       |               |       |
|   A   |               |   X   |
|       |               |       |
|       |               |       |
+-------+               +-------+

Dynamically you can create a one-pixel high image (temp), copy the content from X partially, put it on top of A:

+-------+   +-------+   +-------+
|       |   | temp1 | < |       |
|       |   +-------+   |       |
|   A   |               |   X   |
|       |               |       |
|       |               |       |
+-------+               +-------+

In a loop, dynamically create/resize the temp image, and copy more content from X:

+-------+   +-------+   +-------+
|       |   | temp2 | < |       |
|       |   |       |   |       |
|   A   |   +-------+   |   X   |
|       |               |       |
|       |               |       |
+-------+               +-------+

+-------+   +-------+   +-------+
|       |   | temp3 | < |       |
|       |   |       |   |       |
|   A   |   |       |   |   X   |
|       |   +-------+   |       |
|       |               |       |
+-------+               +-------+
+-------+   +-------+   +-------+
|       |   | temp4 | < |       |
|       |   |       |   |       |
|   A   |   |       |   |   X   |
|       |   |       |   |       |
|       |   +-------+   |       |
+-------+               +-------+

+-------+   +-------+   +-------+
|       |   | tempX | < |       |
|       |   |       |   |       |
|   A   |   |       |   |   X   |
|       |   |       |   |       |
|       |   |       |   |       |
+-------+   +-------+   +-------+

Answer 6

Use an animation block like so:

imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 0)];
imageView.image = ...;
[imageView setClipsToBounds:YES];
[imageView setContentMode:UIViewContentModeTop];

[self.view addSubview:imageView];
[imageView release];

[UIView animateWithDuration:4.0f
                      delay:1.0f
                    options:UIViewAnimationOptionCurveEaseIn
                 animations:^(void) {
                     imageView.frame = CGRectMake(0, 0, 320, 480);
                 }
                 completion:NULL];