ImageResize
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In the age of multi-megapixel images and high concurrency websites it's not practical to take the 
traditional approach to image manipulation that we so commonly see.

The traditional approach is:

 * Load entire image into memory
 * Create a new buffer of the target size
 * Run resampling algorithm which copies from Original to Resampled buffers
 * Discard original buffer
 * Save resampled buffer to target format (PNG, JPEG etc.)

Most camera phones today come with 4MP or higher cameras, which as an RGB buffer is already 11 MiB.
At 12MP it's already over to 35 MiB, there are a surprising number of consumer level devices already on the market
with 12MP or larger sensors.

My revised approach is to read only the scanlines required to produce one scanline in the output file and
to re-use them as needed. This requires only the absolute minimum amount of memory and in practice has
been significantly faster (even with the fork overhead) than PHP+gd or imagemagick.