"Learning iOS: UI series" Modifying the size of a picture operation

1. Add picture operation with UIImage object when adding picture operation

1.[uiimage imagename:@ "1.png"]

2.[uiimage imagewithcontentsoffile:@ "1.png"]

Note: The difference between imagenamed and Imagewithcontentsoffile

Imagenamed loads the image and caches it, and caches the image in memory, using imagenamed when the image is small and frequently used;
Imagewithcontentsoffile is to display only pictures, but not in memory. So when loading a lot of pictures with imagewithcontentsoffile better, the memory will not become larger.

when adding a picture operation, first modify the image size, as follows :

Note: This is the category extension class for UIImage

①uiimage+scale.h declaration file, passing in a cgsize parameter, that is, the width and height of the picture

<span style= "FONT-SIZE:14PX;" >-(UIImage *) Scaletosize: (cgsize) size;</span>

②.m files, implementing Files

<span style= "FONT-SIZE:14PX;" >  //Specify reduced size-(UIImage *) Scaletosize: (cgsize) Size {    //Create a bitmap context    //and set it as the currently in use context    uigraphicsbeginimagecontext (size);    Draw a picture that changes size    [self drawinrect:cgrectmake (0,0, Size.width, Size.Height)];    Creates a resized image from the current context    UIImage * scaledimage = Uigraphicsgetimagefromcurrentimagecontext ();    Make the current context out of the stack    uigraphicsendimagecontext ();    Returns the new resized picture return    scaledimage;} </span>

method calls, as follows.

<span style= "FONT-SIZE:14PX;" >uiimage *image = [UIImage imagewithcontentsoffile:@ "1.png"];image = [Image Scaletosize:cgsizemake (30, 30)]; Uiimageview *imgeview = [[Uiimageview alloc] Initwithimage:image];</span>

"Learning iOS: UI series" Modifying the size of a picture operation