JAVA后台，将一个base64的字符串通过GZIP压缩成了另一个字符串，iOS端需要先解压，然后转为base64，最后转成图片。找到一个NSData解压的方法，就先把字符串original转成NSdata，解压，然后转回字符串result，这个result就是original解压出来的字符串。转成图片，OK。下面是代码。
//后台返回的字符串
NSString * original = dict[@"imgblob"];
//字符串转NSdata，注意编码格式
NSData * dataGzip = [original dataUsingEncoding:NSISOLatin1StringEncoding];
//解压
NSData * uncompress = [LFCGzipUtillity uncompressZippedData:dataGzip];
//将解压出来的NSdata转成NSString（这就是后台传过来的字符串经过解压处理后的结果字符串）
NSString * result = [[NSString alloc] initWithData:uncompress encoding:NSISOLatin1StringEncoding];
//将这个字符串（是经过base64转码的字符串）转为NSdata
NSData * data =[[NSData alloc] initWithBase64EncodedString:result options:NSDataBase64DecodingIgnoreUnknownCharacters];
//NSdata转为UIimage
UIImage * image = [UIImage imageWithData:data];
_sceneControlImg.image = image;
解压方法如下
+(NSData *)uncompressZippedData:(NSData *)compressedData {
if ([compressedData length] == 0) return compressedData;
unsigned full_length = [compressedData length];
unsigned half_length = [compressedData length] / 2;
NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length];
BOOL done = NO;
int status;
z_stream strm;
strm.next_in = (Bytef *)[compressedData bytes];
strm.avail_in = [compressedData length];
strm.total_out = 0;
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
if (inflateInit2(&strm, (15+32)) != Z_OK) return nil;
while (!done) {
// Make sure we have enough room and reset the lengths.
if (strm.total_out >= [decompressed length]) {
[decompressed increaseLengthBy: half_length];
}
strm.next_out = [decompressed mutableBytes] + strm.total_out;
strm.avail_out = [decompressed length] - strm.total_out;
// Inflate another chunk.
status = inflate (&strm, Z_SYNC_FLUSH);
if (status == Z_STREAM_END) {
done = YES;
} else if (status != Z_OK) {
break;
}
}
if (inflateEnd (&strm) != Z_OK) return nil;
// Set real length.
if (done) {
[decompressed setLength: strm.total_out];
return [NSData dataWithData: decompressed];
} else {
return nil;
}
}
另附GZIP压缩方法：
+ (NSData *)gzipData:(NSData *)pUncompressedData
{
if (!pUncompressedData || [pUncompressedData length] == 0) {
NSLog(@"%s: Error: Can't compress an empty or nil NSData object",__func__);
return nil;
}
z_stream zlibStreamStruct;
zlibStreamStruct.zalloc = Z_NULL;
zlibStreamStruct.zfree = Z_NULL;
zlibStreamStruct.opaque = Z_NULL;
zlibStreamStruct.total_out = 0;
zlibStreamStruct.next_in = (Bytef *)[pUncompressedData bytes];
zlibStreamStruct.avail_in = [pUncompressedData length];
int initError = deflateInit2(&zlibStreamStruct, Z_DEFAULT_COMPRESSION, Z_DEFLATED, (15+16), 8, Z_DEFAULT_STRATEGY);
if (initError != Z_OK) {
NSString *errorMsg = nil;
switch (initError) {
case Z_STREAM_ERROR:
errorMsg = @"Invalid parameter passed in to function.";
break;
case Z_MEM_ERROR:
errorMsg = @"Insufficient memory.";
break;
case Z_VERSION_ERROR:
errorMsg = @"The version of zlib.h and the version of the library linked do not match.";
break;
default:
errorMsg = @"Unknown error code.";
break;
}
NSLog(@"%s:deflateInit2() Error: \"%@\" Message: \"%s\"",__func__,errorMsg,zlibStreamStruct.msg);
return nil;
}
NSMutableData *compressedData = [NSMutableData dataWithLength:[pUncompressedData length] * 1.01 + 21];
int deflateStatus;
do {
zlibStreamStruct.next_out = [compressedData mutableBytes] + zlibStreamStruct.total_out;
zlibStreamStruct.avail_out = [compressedData length] - zlibStreamStruct.total_out;
deflateStatus = deflate(&zlibStreamStruct, Z_FINISH);
} while (deflateStatus == Z_OK);
if (deflateStatus != Z_STREAM_END)
{
NSString *errorMsg = nil;
switch (deflateStatus) {
case Z_ERRNO:
errorMsg = @"Error occured while reading file.";
break;
case Z_STREAM_ERROR:
errorMsg = @"The stream state was inconsistent (e.g., next_in or next_out was NULL).";
break;
case Z_DATA_ERROR:
errorMsg = @"The deflate data was invalid or incomplete.";
break;
case Z_MEM_ERROR:
errorMsg = @"Memory could not be allocated for processing.";
break;
case Z_BUF_ERROR:
errorMsg = @"Ran out of output buffer for writing compressed bytes.";
break;
case Z_VERSION_ERROR:
errorMsg = @"The version of zlib.h and the version of the library linked do not match.";
break;
default:
errorMsg = @"Unknown error code.";
break;
}
NSLog(@"%s:zlib error while attempting compression: \"%@\" Message: \"%s\"", __func__, errorMsg, zlibStreamStruct.msg);
deflateEnd(&zlibStreamStruct);
return nil;
}
deflateEnd(&zlibStreamStruct);
[compressedData setLength:zlibStreamStruct.total_out];
NSLog(@"%s: Compressed file from %d B to %d B", __func__, [pUncompressedData length], [compressedData length]);
return compressedData;
}
