IOS zooms in or out images by gesture

1. Add a variable to the. h file to record the current scale value so that the viewcontroller follows

Uigesturerecognizerdelegate proxy.

Add the following variable to. h.

Cgfloat lastscale;

2. Add the following statement to viewdidload:

Uiview * holderview = [[uiviewalloc] initwithframe: cgrectmake (0, 0, 320,
(416)];

Uiimageview * showimgview = [[uiimageviewalloc] initwithframe: cgrectmake (0, 0, 320,
(416)];

Showimgview. Image = IMG;

Showimgview. contentmode = uiviewcontentmodescaleaspectfit;

[Holderview
Addsubview: showimgview];

[Showimgview
Release];

Uipinchgesturerecognizer * pinchrecognizer = [[uipinchgesturerecognizeralloc] initwithtarget: selfaction: @ selector (scagesture :)];

[Pinchrecognizersetdelegate: Self];

[Holderview
Addgesturerecognizer: pinchrecognizer];

[Pinchrecognizerrelease];

[Self. viewaddsubview: holderview];

[Holderview
Release];

3. How to execute this gesture

-(Void) scagesture :( ID) sender {

[Self. viewbringsubviewtofront: [(uipinchgesturerecognizer *) senderview];

// Set lastscale to 1.0 when the finger leaves the screen

If ([(uipinchgesturerecognizer *) senderstate]
= Uigesturerecognizerstateended ){

Lastscale = 1.0;

Return;

}

Cgfloat scale = 1.0-(lastscale-[(uipinchgesturerecognizer *) senderscale]);

Cgaffinetransform currenttransform = [(uipinchgesturerecognizer *) senderview]. Transform;

Cgaffinetransform newtransform = cgaffinetransformscale (currenttransform, scale, scale );

[[(Uipinchgesturerecognizer *) senderview] settransform: newtransform];

Lastscale = [(uipinchgesturerecognizer *) senderscale];

}

4. Proxy Method for adding gestures

# Pragma mark-uigesturerecognizerdelegate

-(Bool) gesturerecognizer :( uigesturerecognizer *) gesturerecognizer

Shouldrecognizesimultaneouslywithgesturerecognizer :( uigesturerecognizer *) othergesturerecognizer {

Return! [Gesturerecognizer iskindofclass: [uipangesturerecognizerclass];

}

5. Run the program and the effect (note that only images in the image center can be zoomed in, But images cannot be moved. To move images, You need to modify part of its transform code)

The figure below is from somewhere else,
Uploading on your own is troublesome.

Note: Please run on the real machine. The pinch gesture cannot be simulated in the simulator. You can also press and hold the option and shift keys to simulate the gesture of two fingers on the simulator.