iOS set up a picture to enlarge the effect

For example, in TableView's head set a picture, pull down tableview, the above picture will show the effect of magnification.

First define the Uiimageview, set the relevant parameters

Static . F;

Expandzoomimageview = [[Uiimageview alloc] Initwithframe:cgrectmake (0,-= [UIImage imagenamed:@ "laracroft.png"= Uiviewcontentmodescaleaspectfill;

Self. TableView. Contentinset = Uiedgeinsetsmake(kimageoriginhight, 0, 0, 0 );

[self. TableView addsubview: Expandzoomimageview];

After setting up the TableView agent, add the enlarged action on the agent of scroll

-(void) Scrollviewdidscroll: (Uiscrollview *) scrollview{    cgfloat yoffset  =  Scrollview.contentoffset.y;     if (Yoffset <-kimageoriginhight) {        = self.expandZoomImageView.frame;         = Yoffset;         =  -yoffset;         = f;    }}

This will make the picture have a magnified effect when the TableView is pulled down.

Among them, ImageView Contentmode in the default case is Uiviewcontentmodescaletofill, will cause the picture deformation , all related variables such as long, wide need to set their own;

Uiviewcontentmodescaleaspectfit will ensure that the picture scale is not changed, but is filled with the entire ImageView, may only part of the picture display; Uiviewcontentmodescaleaspectfill guarantee that the picture scale is the same, but it fills the entire ImageView, and maybe only some of the pictures are displayed.

Reference Demo:https://github.com/lidechao/expandzoom

iOS set up a picture to enlarge the effect