Issue in Coverting zlib compressed base64 string t

问题:

In one my current project, I have to parse base 64 string, which is encoded and stored by flex(Adobe Flash) application. By discussing with flex dev team I found that they storing image string in bitmap format so I assumed it is a pixel representation.

So, first question from me is, in above mentioned case can I directly convert raw data into UIimage using base64 decoding class or I have to use CGBitmapContext ?

However, currently I have implemented below mentioned code for conversion.

` //Convert to Base64 data

NSData *decodedData = [QSStrings decodeBase64WithString:_settingSerializedImage.currentValue];


NSError *error = nil;
NSData *unCompressedData = [decodedData bbs_dataByInflatingWithError:&error];



NSData *dataImage = [NSMutableData new];
NSUInteger bytePosition = 0;
uint8_t * bytes =  malloc(5);
[unCompressedData getBytes:&bytes range:NSMakeRange(unCompressedData.length-3, 3)];

bytes = OSSwapBigToHostInt16(bytes);
int width = (int)bytes;

[unCompressedData getBytes:&bytes range:NSMakeRange(unCompressedData.length-5, 5)];

bytes = OSSwapBigToHostInt16(bytes);dataImage = [unCompressedData subdataWithRange:NSMakeRange(0, (unCompressedData.length -5))];

NSUInteger length = [dataImage length];
unsigned char *bytesData = malloc( length * sizeof(unsigned char) ); [dataImage getBytes:bytesData length:length];UIImage *imgScreenShot = [ScreenshotPortlet convertBitmapRGBA8ToUIImage:bytesData withWidth:width withHeight:height];`

below is the method for converting raw data in image using core graphics

+ (UIImage *) convertBitmapRGBA8ToUIImage:(unsigned char *) buffer
                            withWidth:(int) width
                           withHeight:(int) height {

 char* rgba = (char*)malloc(width*height*4);
for(int i=0; i < width*height; ++i) {
    rgba[4*i] = buffer[4*i];
    rgba[4*i+1] = buffer[4*i+1];
    rgba[4*i+2] = buffer[4*i+2];
    rgba[4*i+3] = buffer[4*i+3];
}
//


size_t bufferLength = width * height * 4;
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, rgba, bufferLength, NULL);
size_t bitsPerComponent = 8;
size_t bitsPerPixel = 32;
size_t bytesPerRow = 4 * width;

CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
  if(colorSpaceRef == NULL) {
    NSLog(@"Error allocating color space");
    CGDataProviderRelease(provider);
    return nil;
}

CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedFirst;

CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGImageRef iref = CGImageCreate(width,
                                height,
                                bitsPerComponent,
                                bitsPerPixel,
                                bytesPerRow,
                                colorSpaceRef,
                                bitmapInfo,
                                provider,
                                NULL,
                                YES,
                                renderingIntent);

uint32_t* pixels = (uint32_t*)malloc(bufferLength);

if(pixels == NULL) {
    NSLog(@"Error: Memory not allocated for bitmap");
    CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpaceRef);
    CGImageRelease(iref);
    return nil;
}

CGContextRef context = CGBitmapContextCreate(pixels,
                                             width,
                                             height,
                                             bitsPerComponent,
                                             bytesPerRow,
                                             colorSpaceRef,
                                             bitmapInfo);

if(context == NULL) {
    NSLog(@"Error context not created");
    free(pixels);
}

UIImage *image = nil;
if(context) {

    CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), iref);

    CGImageRef imageRef = CGBitmapContextCreateImage(context);

    image = [UIImage imageWithCGImage:imageRef];

    CGImageRelease(imageRef);
    CGContextRelease(context);
}

CGColorSpaceRelease(colorSpaceRef);
CGImageRelease(iref);
CGDataProviderRelease(provider);


if(pixels) {
    free(pixels);
}   
return image;

}

Here is the output I'm getting , a distorted image :

So can anyone suggest me better solution or tell if I'm on right direction in it or not? Thanks, in advance :)

For reference here you can find original base 64 string

回答1:

To convert image to base64string:

- (NSString *)imageToNSString:(UIImage *)image
{
    NSData *data = UIImagePNGRepresentation(image);

    return [data base64EncodedStringWithOptions:NSDataBase64EncodingEndLineWithLineFeed];
}

To convert base64string to image:

- (UIImage *)stringToUIImage:(NSString *)string
{
    NSData *data = [[NSData alloc]initWithBase64EncodedString:string options:NSDataBase64DecodingIgnoreUnknownCharacters];

    return [UIImage imageWithData:data];
}