[Digikam-devel] So cool! exiftool adds metatag writing support for png files

[Thorsten Schnebeck]

Hi,

in the latest devel snapshot of exiftool 
(http://www.sno.phy.queensu.ca/~phil/exiftool) Phil adds metatag 
writing support for png files!!!

Now it is possible to use a loseless image format and also saving 
your metatags. Its simple as

exiftool -TagsFromFile Photo-0015.jpg  Photo-0015.png
    1 image files updated

Lets look at png metatags:

exiftool  Photo-0015.png

exiftool Photo-0015.png
ExifTool Version Number         : 5.63
File Name                       : Photo-0015.png
File Size                       : 2282KB
File Modification Date/Time     : 2005:04:12 15:15:06
File Type                       : PNG
MIME Type                       : image/png
Bit Depth                       : 8
Color Type                      : RGB
Filter                          : Adaptive
Interlace                       : Noninterlaced
Significant Bits                : 8 8 8
Make                            : Canon
Camera Model Name               : Canon DIGITAL IXUS v
Orientation                     : Horizontal (normal)
X Resolution                    : 180
Y Resolution                    : 180
Resolution Unit                 : inches
Date/Time Of Last Modification  : 2005:04:12 13:15:07
Y Cb Cr Positioning             : Centered
Shutter Speed                   : 1/60
Aperture                        : 7.2
Exif Version                    : 0210
Shooting Date/Time              : 2005:04:12 13:15:07
Date/Time Of Digitization       : 2005:04:12 13:15:07
Components Configuration        : YCbCr
Compressed Bits Per Pixel       : 5
Shutter Speed Value             : 1/60
Aperture Value                  : 7.3
Max Aperture Value              : 2.8
Subject Distance                : 0.461 m
Flash                           : Fired
Focal Length                    : 5.4mm
Macro Mode                      : Normal
Self-timer                      : 0
Image Quality                   : Superfine
Canon Flash Mode                : Auto
Continuous Drive                : Single
Focus Mode                      : Single
Canon Image Size                : Large
Easy Mode                       : Full auto
Digital Zoom                    : None
Camera ISO                      : Use shot ISO instead
Metering Mode                   : Evaluative
Focus Type                      : Auto (1)
AF Point                        : Auto-selected
Canon Exposure Mode             : Easy
Lens Type                       : Unknown (-1)
Long Focal                      : 346
Short Focal                     : 173
Focal Units                     : 32
Max Aperture                    : 2.9
Flash Bits                      : Internal flash
Focus Continuous                : Single
Zoomed Resolution               : 1600
Zoomed Resolution Base          : 1600
Focal Plane X Size              : 5.36mm
Focal Plane Y Size              : 4.01mm
ISO Speed                       : 69
Target Aperture                 : 7.1
Target Exposure Time            : 1/60
Exposure Compensation           : 0
White Balance                   : Auto
Shot Number In Continuous Burst : 1
Ixus AF Point                   : Left+Right
Flash Exposure Compensation     : 0
Auto Exposure Bracketing        : Off
AEB Bracket Value               : 0
Focus Distance Upper            : 4.61
Focus Distance Lower            : 0
Bulb Duration                   : 0
Canon Image Type                : IMG:DIGITAL IXUS v JPEG
Canon Firmware Version          : Firmware Version 1.0
File Number                     : 100-0015
User Comment                    :
Flashpix Version                : 0100
Color Space                     : sRGB
Exif Image Width                : 1600
Exif Image Length               : 1200
Interoperability Index          : R98
Interoperability Version        : 0100
Related Image Width             : 1600
Related Image Length            : 1200
Focal Plane X Resolution        : 7766.99
Focal Plane Y Resolution        : 7741.94
Focal Plane Resolution Unit     : inches
Sensing Method                  : One-chip color area
File Source                     : Digital Camera
Contrast                        : Normal
Saturation                      : Normal
Sharpness                       : Normal
Owner's Name                    : schnebeck
Thumbnail Offset                : 1306
Thumbnail Length                : 5164
Compression                     : JPEG (old-style)
Image Height                    : 1200
Image Width                     : 1600
Aperture                        : 7.2
Flash Exposure Compensation     : 0
Drive Mode                      : Single-frame shooting
Flash                           : On
Flash Type                      : Built-In Flash
Image Size                      : 1600x1200
Lens                            : 5.4 - 10.8mm
Red Eye Reduction               : Off
Scale Factor To 35mm Equivalent : 6.6
Shooting Mode                   : Full auto
Shutter Curtain Sync            : 1st-curtain sync
Shutter Speed                   : 1/60
Thumbnail Image                 : (Binary data 5164 bytes, use -b 
option to extract)
Circle Of Confusion             : 0.005 mm
Focal Length                    : 5.4mm (35mm equivalent: 35.7mm)
Hyperfocal Distance             : 0.89 m
Lens                            : 5.4 - 10.8mm (35mm equivalent: 
35.7 - 71.4mm)

And please remember, when digiKam switches to 16bit/channel you 
can not use JPEG any longer and here also PNG is a strong format. 
As you can also edit, copy, add, delete any kind of tag in 
(nearly) any kind of image format, I still believe digiKam and/or 
kipi need somehow an interface to this 1st-class-perllib. :-) 
Think of a camera interface automatically switching from jpg to 
png keeping all metatags or a rawconverter saving result as 
png/16bit with all tags! And now there is no reason any longer to 
keep user tag only in a database but also in the file. Think of 
all the poor Canon 20D-Users that need to change their DPI-Tag 
from 72 to 300 when selling photos...

Bye

  Thorsten