[Clipart] The PNG problem in Windows Internet Explorer

[Glenn Randers-Pehrson]

At 11:17 PM 1/22/2005 -0800, Jon Phillips wrote:
>Glenn Randers-Pehrson wrote:
>> At 10:08 AM 1/21/2005 -0500, Jonadab the Unsightly One wrote:
>> 
>>>Salvatore Davide Rapisarda <blackmicio at tiscali.it> writes:
>>>
>>>
>>>>The problem is that explorer ignore alpha transparency in a png
>>>>image,
>>>
>>>Didn't somebody here post a method for using a PNG-related
>>>command-line tool, pngcrunch or something like that, to fix an PNG
>>>image so that it would display more correctly on IE, without changing
>>>its appearance for standards-conformant browsers and image editors?
>>>
>>>Hang on, maybe I can dig it up...
>>>
>>>Message-Id: <3.0.6.32.20041113110721.0118ec78 at mail.comcast.net>
>>>
>>># See
>>>#                                                                                                                  
>>># http://www.graphicsmagick.org/libpng/ocal/openclipart.org.html
>>># which compares the original and the "sRGB" versions.  With Firefox
>>># they look the same, but with IE one is a lot darker than the other.
>>>#                                                                                                                  
>>># I used pngcrush to remove the gAMA chunk and add the sRGB chunk:
>>>#                                                                                                                  
>>>#   pngcrush -rem gama -srgb 1 -rem gama ocal-header.png ocal-header-sRGB.png
>>>#                                                                                                                  
>>># As a side benefit, the file is 3.5kbytes smaller.
>>>#                                                                                                                  
>>># Glenn
>> 
>> 
>> This fixes the IE bug with color-matching but not the IE bug with
>> transparency.
>> 
>> Glenn
>> 
>> 
>>>If we did this to the PNG thumbnails in the package,
>>>1.  Would it improve the appearance of the site (especially the
>>>    browse portion) in MSIE?
>>>2.  Would it have any downside, e.g., impact on other
>>>    browsers or remove wanted information from the images?
>>>
>>>It could be a little computation-intensive, but that is not a big
>>>problem if we do it just once to each batch of images as part of the
>>>release cycle.  I mean, generating the thumbnails in the first place
>>>is a bit CPU-intensive, but so what?
>
>
>Thanks for this fix. I went ahead and copied what you did to the main website. I 
>think it would be wise to process each image to thumnail in the gallery this 
>way. What do we need to move over to the server or have installed to run this app?

pngcrush itself is a single c file.  It depends on libpng and zlib.
It can be installed with the libraries statically loaded (included in
the pngcrush executable) which is porbably the simplest way.

Glenn