JPG File Size Optimization - PHP, ImageMagick, & Google's Page Speed

Question

I have photo gallery code that does image re-sizing and thumbnail creation. I use ImageMagick to do this. I ran a gallery page through Google's Page Speed tool and it revealed that the re-sized images and thumbnails both have about an extra 10KB of data (JPEG files specifically).

What can I add to my scripts to optimize the file size?

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ADDITIONAL INFORMATION

I am using the imagick::FILTER_LANCZOS filter with a blur setting of 0.9 when calling the resizeImage() function. JPEGs have a quality setting of 80.

Answer 1

I found this SO question, "Tools for JPEG optimization?", that has some good information, but the solutions are outside of PHP. Using hints from that question's solutions I found that there were two lossless optimizations that could be performed:

1. Optimization of the Huffman coding tables
2. Removal of meta-data (EXIF, etc)

Both of can be accomplished with ImageMagick this way:

1. According to ImageMagick documentation, the optimal Huffman coding tables are computed by default. This step is already taken care of, yay!
2. Removal of meta-data can be accomplished very simply by using the stripImage() method.

One image I tested was reduced by 12KB. The 600x450 file went from 63.42KB to 51.42KB, and the 140x105 thumbnail went from 17.98KB to 5.98KB.

Answer 2

Run your images through Yahoo's SmushIt service, where the images are converted to a PNG with an exact number of colors. No loss in quality, but a loss in weight :)