Compressing Images in Iphone programmatically from NSData - iphone

Question

I wish to compress the image before storing it as an NSData object.
Below is the code, that helps me take NSData object of an Image.
NSURL *referenceURL = [info objectForKey:UIImagePickerControllerReferenceURL];
ALAssetsLibrary *library1 = [[ALAssetsLibrary alloc] init];
[library1 assetForURL:referenceURL resultBlock:^(ALAsset *asset)
{
int byteArraySize = asset.defaultRepresentation.size;
NSMutableData* rawData = [[NSMutableData alloc]initWithCapacity:byteArraySize];
void* bufferPointer = [rawData mutableBytes];
NSError* error=nil;
[asset.defaultRepresentation getBytes:bufferPointer fromOffset:0 length:byteArraySize error:&error];
if (error) {
NSLog(#"%#",error);
}
rawData = [NSMutableData dataWithBytes:bufferPointer length:byteArraySize];
}
Any Help will be appreciated.

Answer 1

UIImagePickerController does return a compressed image, but you can control the format and compression as well with this built in UIKit function and a related function for PNGs:
NSData* UIImageJPEGRepresentation(UIImage *image, CGFloat compressionQuality);
You might need to create an NSURL if referenceURL returns a string.
NSImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL: referenceURL]];
NSData *compressedImage = UIImageJPEGRepresentation(image, .1); //.1 is low quality

Answer 2

If you're using a UIImagePickerController, the image returned will be a JPEG, which is already compressed (I think). If not, you can use AVAssetWriter to write the image as a JPEG or PNG.

Answer 3

simple to use:-
-(UIImage *)fireYourImageForCompression:(UIImage *)imgComing{
NSData *dataImgBefore = [[NSData alloc] initWithData:UIImageJPEGRepresentation((imgComing), 1.0)];//.1 BEFORE COMPRESSION
int imageSizeBefore = (int)dataImgBefore.length;
NSLog(#"SIZE OF IMAGE: %i ", imageSizeBefore);
NSLog(#"SIZE OF IMAGE in Kb: %i ", imageSizeBefore/1024);
NSData *dataCompressedImage = UIImageJPEGRepresentation(imgComing, .1); //.1 is low quality
int sizeCompressedImage = (int)dataCompressedImage.length;
NSLog(#"SIZE AFTER COMPRESSION OF IMAGE: %i ", sizeCompressedImage);
NSLog(#"SIZE AFTER COMPRESSION OF IMAGE in Kb: %i ", sizeCompressedImage/1024); //AFTER
//now change your image from compressed data
imgComing = [UIImage imageWithData:dataCompressedImage];
return imgComing;}