How to save a TIFF photo from AVFoundations captureStillImageAsynchronouslyFromConnection to a file with EXIF metadata on an iPhone (iOS)?

问题

With this question I only ask for the possibilities I have with Xcode and iOS without external libraries. I am already exploring the possibility of using libtiff in another question.

Problem

I have been sieving stack overflow for weeks and found working solutions for every one of my problems on its own. I have 4 things that need to work:

I need the RGBA data as it comes from the camera, no compression whatsoever
I need as much metadata as possible, especially EXIF
I need to save in TIFF format for compatibility with other software and losslessness
I need protection from casual viewing by saving in a file, not the photo library

I can have 2 and 4 by using JPEG. I can have 1, 3 and 4 with raw data (respectively NSData) made from the camera buffer. Can I have all 4 of my prerequisites with Xcode and iOS? I am about to give up and looking for your input as a last resort.

While still exploring this, I am also stuck on the other avenue I tried, libtiff. I am still trying, though...

Here is the list of great advice I have tried, my own code is just put together from stack overflow sources like these:

How to write exif metadata to an image (not the camera roll, just a UIImage or JPEG) (makes me wish I could use JPEG format, it is so effortless when doing what Apple prefers)
Raw image data from camera like “645 PRO” (this would be the point to use e.g. libtiff)
Saving CGImageRef to a png file? (works with kUTTypeTIFF, too, but no metadata)

Solution

The complete sequence of actions from captureStillImageAsynchronouslyFromConnection:

[[self myAVCaptureStillImageOutput] captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error)
 {
     //get all the metadata in the image
     CFDictionaryRef metadata = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, imageSampleBuffer, kCMAttachmentMode_ShouldPropagate);
     // get image reference
     CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(imageSampleBuffer);
     // >>>>>>>>>> lock buffer address
     CVPixelBufferLockBaseAddress(imageBuffer, 0);

     //Get information about the image
     uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);
     size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
     size_t width = CVPixelBufferGetWidth(imageBuffer);
     size_t height = CVPixelBufferGetHeight(imageBuffer);

     // create suitable color space
     CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

     //Create suitable context (suitable for camera output setting kCVPixelFormatType_32BGRA)
     CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);

     // <<<<<<<<<< unlock buffer address
     CVPixelBufferUnlockBaseAddress(imageBuffer, 0);

     // release color space
     CGColorSpaceRelease(colorSpace);

     //Create a CGImageRef from the CVImageBufferRef
     CGImageRef newImage = CGBitmapContextCreateImage(newContext);

     // release context
     CGContextRelease(newContext);

     // create destination and write image with metadata
     CFURLRef url = (__bridge CFURLRef)[NSURL fileURLWithPath:filePath isDirectory:NO];
     CGImageDestinationRef destination = CGImageDestinationCreateWithURL(url, kUTTypeTIFF, 1, NULL);
     CGImageDestinationAddImage(destination, imageRef, metadata);

     // finalize and release destination
     CGImageDestinationFinalize(destination);
     CFRelease(destination);
 }

The still image output related camera settings were:

[[self myAVCaptureSession] setSessionPreset:AVCaptureSessionPresetPhoto];

and

NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA], (id)kCVPixelBufferPixelFormatTypeKey, nil];
[myAVCaptureStillImageOutput setOutputSettings:outputSettings];

I get a nice nominally uncompressed image in nominal TIFF format with all metadata. (It is mirrored on other systems, but now I can write the EXIF and other metadata, I can also fine-tune that, I am sure).

Thanks again to Wildaker for his help!

回答1:

As you've already cracked 1, 3 and 4, it seems the only hurdle you're missing is saving the data and metadata together. Try this (assuming the unprocessed data is in a CMSampleBufferRef called myImageDataSampleBuffer and you've done the heavy lifting of putting the graphical data into a CGImageRef called myImage):

CFDictionaryRef metadata = CMCopyDictionaryOfAttachments(kCFAllocatorDefault,
  myImageDataSampleBuffer,
  kCMAttachmentMode_ShouldPropagate);
NSFileManager* fm = [[NSFileManager alloc] init];
NSURL* pathUrl = [fm URLForDirectory:saveDir
  inDomain:NSUserDomainMask
  appropriateForURL:nil
  create:YES
  error:nil];
NSURL* saveUrl = [pathUrl URLByAppendingPathComponent:@"myfilename.tif"];
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)saveUrl,
  (CFStringRef)@"public.tiff", 1, NULL);
CGImageDestinationAddImage(destination, myImage, metadata);
CGImageDestinationFinalize(destination);
CFRelease(destination);

回答2:

This thread was very helpful in resolving a very similar problem, so I thought I'd contribute a Swift 2.0 implementation of the solution in case someone comes looking.

stillImageOutput?.captureStillImageAsynchronouslyFromConnection(videoConnection, completionHandler: { (imageDataSampleBuffer, error) -> Void in


    // get image meta data (EXIF, etc)
    let metaData: CFDictionaryRef? = CMCopyDictionaryOfAttachments( kCFAllocatorDefault, imageDataSampleBuffer, kCMAttachmentMode_ShouldPropagate )


    // get reference to image
    guard let imageBuffer = CMSampleBufferGetImageBuffer( imageDataSampleBuffer ) else { return }


    // lock the buffer
    CVPixelBufferLockBaseAddress( imageBuffer, 0 )


    // read image properties
    let baseAddress = CVPixelBufferGetBaseAddress( imageBuffer )

    let bytesPerRow = CVPixelBufferGetBytesPerRow( imageBuffer )

    let width = CVPixelBufferGetWidth( imageBuffer )

    let height = CVPixelBufferGetHeight( imageBuffer )


    // color space
    let colorSpace = CGColorSpaceCreateDeviceRGB()


    // context - camera output settings kCVPixelFormatType_32BGRA
    let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue).union(.ByteOrder32Little)

    let newContext = CGBitmapContextCreate( baseAddress, width, height, 8, bytesPerRow, colorSpace, bitmapInfo.rawValue )


    //unlock buffer
    CVPixelBufferUnlockBaseAddress( imageBuffer, 0 )

    //Create a CGImageRef from the CVImageBufferRef
    guard let newImage = CGBitmapContextCreateImage( newContext ) else {
        return
    }


    // create tmp file and write image with metadata
    let fileName = String(format: "%@_%@", NSProcessInfo.processInfo().globallyUniqueString, "cap.tiff")
    let fileURL = NSURL(fileURLWithPath: NSTemporaryDirectory()).URLByAppendingPathComponent(fileName)

    if let destination = CGImageDestinationCreateWithURL( fileURL, kUTTypeTIFF, 1, nil) {

        CGImageDestinationAddImage( destination, newImage, metaData )

        let wrote = CGImageDestinationFinalize( destination )

        if !wrote || NSFileManager.defaultManager().fileExistsAtPath(fileURL.URLString) {

            return

        }

    }

}

p.s. for this to work, you have to configure your image buffer like this:

    stillImageOutput = AVCaptureStillImageOutput()

    stillImageOutput?.outputSettings = [ kCVPixelBufferPixelFormatTypeKey: Int(kCVPixelFormatType_32BGRA) ]

来源：https://stackoverflow.com/questions/17361100/how-to-save-a-tiff-photo-from-avfoundations-capturestillimageasynchronouslyfromc

标签

avfoundation

tiff

exif

nsdocumentdirectory