objective c - Converting image to NSData & back is nil -

when do

uiimage *photo = [uiimage imagenamed:@"sample_thumbnail.png"]; self.thumbnail.image = photo; 

i see thumbnail, png, fine. when convert nsdata & doing:

uiimage *photo = [uiimage imagenamed:@"sample_thumbnail.png"]; nsdata *data = uiimagepngrepresentation(photo); self.photodata = [[nsstring alloc] initwithdata:data encoding:nsutf8stringencoding]; self.thumbnail.image = [uiimage imagewithdata:[self.photodata datausingencoding:nsutf8stringencoding]]; 

self.photodata nil.

why happening?

i think problem way create image nsdata instance. give try 1 instead:

uiimage *photo = [uiimage imagenamed:@"sample_thumbnail.png"]; nsdata *data = uiimagepngrepresentation(photo); uiimage *image = [uiimage imagewithdata:data]; 

__update__

below excerpt this post

- (nsstring *)imagetonsstring:(uiimage *)image {     nsdata *imagedata = uiimagepngrepresentation(image);      return [imagedata base64encodedstringwithoptions:nsdatabase64encoding64characterlinelength]; }  - (uiimage *)stringtouiimage:(nsstring *)string {     nsdata *data = [[nsdata alloc]initwithbase64encodedstring:string                                                   options:nsdatabase64decodingignoreunknowncharacters];      return [uiimage imagewithdata:data]; }