iPhone XIB quickly grows to huge size

Question

I used to have a very small/simple XIB file.
Something has caused it to quickly grow to over 500k.

The only graphics in it are 3 small PNG files (about 4k each).

Here's some of the XIB. Any idea on what is causing this size increase?

   <string key="NSFrame">{{0, 44}, {320, 416}}</string>
                        <reference key="NSSuperview" ref="391473517"/>
                        <object class="NSColor" key="IBUIBackgroundColor">
                            <int key="NSColorSpace">10</int>
                            <object class="NSImage" key="NSImage">
                                <int key="NSImageFlags">469473884</int>
                                <string key="NSSize">{256, 256}</string>
                                <object class="NSMutableArray" key="NSReps">
                                    <bool key="EncodedWithXMLCoder">YES</bool>
                                    <object class="NSArray">
                                        <bool key="EncodedWithXMLCoder">YES</bool>
                                        <integer value="0"/>
                                        <object class="NSBitmapImageRep">
                                            <object class="NSData" key="NSTIFFRepresentation">
                                                <bytes key="NS.bytes">
anB3/3Byef91d33/dHZ8/2psc/9sbnX/Z2p0/3N1fP9qbXf/cXN6/2psdf9wcnv/dnd9/25xe/9ucHf/
cnB3/2ptd/92eH//a254/3Fzev9sb3n/cHJ5/25wd/9ucHf/cHN9/25wd/9wcnn/dnh8/2xudf93eX//
bm13/2ptd/9sb3n/bG51/3V3ff97fYP/YmVu/25xe/9sb3n/c3Z//2psc/9zdXz/cHN9/2dqcf9qbHP/
CmVu/2dqdP9nanH/am13/2xvef91eIH/Z2p0/25xe/91d33/bG51/25wd/92eHz/dXd9/29xdf9ucHf/
fHl9/2xudf9ucHf/bG95/3Bzff9sb3n/bnF7/3l7gf9zdn//c3Z//3N2f/91eIH/c3V8/3Byef9nanT/
zXd9/2dqdP9ucXv/dXd9/3N2f/9zdXz/Z2px/2xudf9ucXv/am13/3Bzff9zdXz/cHN9/2psc/9qbXf/
AbG51/2Jlbv9qbXf/aGp0/2hqcP9rbnX/cnV//29yfP9ucXv/bnF7/25xe/9zdn//bXB1/2xvef9qbXb/

Answer 1

They might have been PNG files that you dragged in, but the xib contains TIFF data:

<object class="NSData" key="NSTIFFRepresentation">

You should remove the images from your nib and include the PNG files in your application bundle and refer to them by name from your code.

(That's assuming, of course, that the small snippet of xib you showed is actually relevant to the problem, and not something completely innocent.)