Apr 30, 2010 2
image caching in iphone sdk
If you’re pulling in web data such as images that doesn’t change but needs to be viewed multiple times, you’ll want to cache it. Caching images dramatically improves the performance of scrolling tables and other views.
Here is a very simple class, with which you can implement caching of images in your iPhone app.
ImgCache.h :
#import <UIKit/UIKit.h>
@interface ImgCache : NSObject {
}
- (void) cacheImage: (NSString *) ImageURLString;
- (UIImage *) getImage: (NSString *) ImageURLString;
@end
ImgCache.m :
#import "ImgCache.h"
#define TMP NSTemporaryDirectory()
@implementation ImgCache
- (void) cacheImage: (NSString *) ImageURLString
{
NSURL *ImageURL = [NSURL URLWithString: ImageURLString];
//generating unique name for the cached file with ImageURLString so you can retrive it back
NSMutableString *tmpStr = [NSMutableString stringWithString:ImageURLString];
[tmpStr replaceOccurrencesOfString:@"/" withString:@"-" options:1 range:NSMakeRange(0, [tmpStr length])];
NSString *filename = [NSString stringWithFormat:@"%@",tmpStr];
NSString *uniquePath = [TMP stringByAppendingPathComponent: filename];
// Check for file existence
if(![[NSFileManager defaultManager] fileExistsAtPath: uniquePath])
{
// The file doesn't exist, we should get a copy of it
// Fetch image
NSData *data = [[NSData alloc] initWithContentsOfURL: ImageURL];
UIImage *image = [[UIImage alloc] initWithData: data];
// Is it PNG or JPG/JPEG?
// Running the image representation function writes the data from the image to a file
if([ImageURLString rangeOfString: @".png" options: NSCaseInsensitiveSearch].location != NSNotFound)
{
[UIImagePNGRepresentation(image) writeToFile: uniquePath atomically: YES];
}
else if(
[ImageURLString rangeOfString: @".jpg" options: NSCaseInsensitiveSearch].location != NSNotFound ||
[ImageURLString rangeOfString: @".jpeg" options: NSCaseInsensitiveSearch].location != NSNotFound
)
{
[UIImageJPEGRepresentation(image, 100) writeToFile: uniquePath atomically: YES];
}
}
}
- (UIImage *) getImage: (NSString *) ImageURLString
{
NSMutableString *tmpStr = [NSMutableString stringWithString:ImageURLString];
[tmpStr replaceOccurrencesOfString:@"/" withString:@"-" options:1 range:NSMakeRange(0, [tmpStr length])];
NSString *filename = [NSString stringWithFormat:@"%@",tmpStr];
NSString *uniquePath = [TMP stringByAppendingPathComponent: filename];
UIImage *image;
// Check for a cached version
if([[NSFileManager defaultManager] fileExistsAtPath: uniquePath])
{
NSData *data = [[NSData alloc] initWithContentsOfFile:uniquePath];
image = [[UIImage alloc] initWithData:data] ; // this is the cached image
}
else
{
// get a new one
[self cacheImage: ImageURLString];
NSData *data = [[NSData alloc] initWithContentsOfURL:uniquePath];
image = [[UIImage alloc] initWithData:data];
}
return image;
}
@end
