Robert asked:

> In the following, how can I know which initWithImageProperties properties I can set initially, for any given file type?



Robert,

Since you are attempting to save an NSImage, you need to embed it with the appropriate metadata.
prior to saving it. This can be done using NSBitmapImageRep.

Study the techniques here:

http://stackoverflow.com/questions/9231682/how-do-i-set-the-pixels-per-inch-for-an-exported-jpeg-image-in-a-cocoa-app

and the following located near the bottom of the page here:

http://www.cocoabuilder.com/archive/cocoa/313457-drawing-1-bit-images-and-image-resolution.html

-(NSData *)oneBitData:(NSImage *)inputNSImage
{
//output a 1 bit image of NSData format from an NSImage given in gray mode
//get an image rep from the current qrImage
NSSize oldSize = [inputNSImage size];
NSBitmapImageRep *imgRep = [NSBitmapImageRep imageRepWithData:[inputNSImage TIFFRepresentation]];
int
row, column,
widthInPixels = [imgRep pixelsWide],
heightInPixels = [imgRep pixelsHigh];
NSUInteger lePixel;
NSBitmapImageRep *newRep = [[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:nil
pixelsWide:widthInPixels
pixelsHigh:heightInPixels
bitsPerSample:1
samplesPerPixel:1
hasAlpha:NO
isPlanar:YES
colorSpaceName:NSDeviceWhiteColorSpace
bytesPerRow:0
bitsPerPixel:1];
[newRep setSize:oldSize];
for (row = 0; row < heightInPixels; row++)
for (column = 0; column <widthInPixels; column++)
{
//get pixel value from grey and put into 1bit
[imgRep getPixel:&lePixel atX:row y:column];
[newRep setPixel:&lePixel atX:row y:column];
}
//FYI this is not an all purpose solution, this will ONLY work with greyscale images
//that are already 1-bit in spirit
NSImage *tempImage = [[NSImage alloc] initWithSize:oldSize];
[tempImage addRepresentation:newRep];
return [NSData dataWithData:[tempImage TIFFRepresentation]];
}

Once you have set the desired metadata in the image, read the Overview section at the top of the following page
to see why you should be handling your images using file references (NSURL, CFURLRef or paths). Image
metadata is automatically captured when file references are used.

https://developer.apple.com/library/mac/#documentation/graphicsimaging/Reference/IKImageView/IKImageView_Reference.html

Ken