Today I came across to a post by Manfred Weber, which points to a discussion at Adobes Alchemy forum. There you will find a great solution published by metalbot for encoding JPEGs using Alchemy. It’s based on a C library for JPEG image compression by IJG and it’s pretty fast (2,7 sec. for 2000 px x 1500px ) !!! Check out the example:

Example

Click the image to see the live example. Feel free to post a comment about your your results!

Download Full Source

I have changed the original C code a little bit for manipulating the quality of an encoded image as well. It’s just one line added to “as3_jpeg_wrapper.gg” (line 78) jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */); Therefore the “as3_jpeg_wrapper.swc” located within the *.zip is recompiled for using this feature in your Flex project via as3_jpeg_wrapper.write_jpeg_file(baSource, WIDTH, HEIGHT, 3, 2, quality);

Full source of the Flex based example above: AlchemyJPEGEncoderFlexExample.zip (Downloads: 1576)

BTW: You will find the original source of all C based classes published by metalbot here.

Tips

I struggled around to set up Alchemy and to recompile the IJG library and the “as3_jpeg_wrapper.swc”. To avoid this, here are some tips:

• Instruction for set up Alchemy by Lee Felarca (zeropointnine). Best instruction I’ve found so far for set up Alchemy.
• Recompiling the SWC of metalbot’s source following its “README.txt” and using its “Makefile” failed: To avoid this issue, after compiling the C library of jpegsrc you have to move the following files to $ALCHEMY_HOME/jpeg/ as well: “jconfig.h”, “jmorecfg.h” and “jpeglib.h”. Check out the comment by notnick here

[UPDATE 06/22/09] There is another great test for encoding images using Alchemy by Mateusz Malczak, which includes an asynchrounous example as well: Alchemy – asynchronous jpeg encoding Thanks to xoestudio for pointing to this via twitter! [UPDATE]

Have fun

-Jens