TweakPNG

TweakPNG is a low-level utility for examining and modifying PNG image files. The current version requires Windows 2000 or higher (XP, Vista, etc.), though it is possible to build a copy that runs on Windows 95/98/ME. In order to use it, you will need to be at least somewhat familiar with the internal format of PNG files. For information about PNG, see the PNG home page.

A screenshot of TweakPNG:

To download TweakPNG, save the following link:

tweakpng-1.4.5.zip (about 450K) 26 Dec 2012

You can also view the README file.

Development is hosted at GitHub.

To install it, extract the files in the ZIP file to a location of your choice (e.g. C:\Program Files\). To run it, open either x86\tweakpng.exe, or, if you’re using an x64 64-bit edition of Windows, x64\tweakpng.exe.

TweakPNG is free software, distributed under the terms of the GNU General Public License (GPL) version 3. The C++ source code for TweakPNG is included the zip file.

History

v1.4.5 (26 Dec 2012) (download):

• Fixes and improvements related to compressed text.
• Changed the viewer’s background color options.

v1.4.4 (24 Aug 2012) (download):

• Improved support for ICC profiles.
• Improved viewer’s image quality for images with partial transparency.

v1.4.3 (6 Mar 2012) (download):

• Maintenance release

v1.4.2 (9 Aug 2011) (download):

• Rewrote the viewer’s PNG decoder. Slightly more accurate gamma correction.
• Updated to libpng 1.5.4.

v1.4.1 (9 Jan 2011) (download):

• Support for 64-bit builds.
• Support for sCAL chunks.
• Allow drag/drop onto viewer window.
• Minor changes to shortcut keys, icons, etc.
• Updated to libpng 1.5.0.

v1.4.0 (5 Jun 2010) (download):

• Full support for oFFs, acTL, fcTL chunks.
• Support for filters (tools that modify the PNG file).
• Added "Close" and "Reopen" menu items.
• Changed the ZIP file structure slightly; now includes a directory name.
• Updated to libpng 1.4.2 and zlib 1.2.5.

v1.3.2 (22 Aug 2009) (download):

• Fixed bugs when restoring the position of auxiliary windows.
• Fixed the context menu position when using multiple monitors.
• Updated to libpng 1.2.39.

v1.3.1 (7 Dec 2008) (download):

• Full support for sTER chunks.
• Read-only support for APNG chunks.
• Less likely to crash if you attempt to edit an incorrectly-sized chunk.
• Updated to libpng 1.2.33.

v1.3.0 (16 Nov 2008) (download):

• Support for iTXt chunks.
• Updated the binary to use the latest versions of zlib and libpng.
• The binary is now a Unicode application.
• For now at least, the package that I’m distributing does not include a binary that runs on Windows 95/98/ME. The only reason for this is that the compiler I used is not capable of creating such binaries.
• Modified the source code to conditionally support Unicode.
• Modified the source code to use "strsafe" string functions.
• Lots of other cleanup of the source code.
• Fixed a couple of small bugs. But more than likely introduced more new bugs than were fixed, due to the aforementioned source code changes.
• Changed license from GPLv2 to GPLv3.

v1.2.1 (11 Dec 2004) (download):

• Updated the binary to use the latest versions of zlib (1.2.2) and libpng (1.2.8).
• Two or three very small improvements and fixes.

v1.2.0 (29 Dec 2003):

• Added an image viewer (Tools->Show Image Viewer). This makes use of another project of mine, PNGDIB.
• Palette editor now used for selecting grayscale background and transparent colors.
• A few other minor changes.

v1.1.2 (24 Nov 2003):

• Option to add TweakPNG to Windows Explorer context menus.
• Warns when you try to exit without saving changes.
• Compiles cleanly in MSVC6.

v1.1.1 (3 Jan 2001):

• Fixed problem with writing wrong CRC after editing IHDR chunk.

v1.1.0 (28 Dec 2000):

• Palette editing, including bKGD and tRNS chunks for paletted images.
• Persistent window sizes and column widths, and persistent position of text chunk editor and palette editor.
• Rearranged some menus
• Edit IHDR chunk (not much reason to do this though...)
• Context menu
• "Combine all IDAT" function
• Fixed some bugs here and there...

v1.0.1 (27 Dec 1999):

• A few minor bugfixes; more graceful handling of most invalid files; automatic validation on Save; uses standard color picker when appropriate (but usually it’s not)

v1.0.0 (3 Dec 1999):

• Initial release

TweakPNG was written by Jason Summers. You may send comments and questions about TweakPNG to jason1@pobox.com.