macbook:ffmpeg memphis$ ./ffmpeg -dsth 720 -sws_flags fast_bilinear -i testpic.jpg testpic-sized.jpg
ffmpeg version 0.10.2 Copyright (c) 2000-2012 the FFmpeg developers
  built on Jul 17 2012 22:04:19 with gcc 4.2.1 (Apple Inc. build 5666) (dot 3)
  configuration: --disable-avfilter --disable-yasm
  libavutil      51. 35.100 / 51. 35.100
  libavcodec     53. 61.100 / 53. 61.100
  libavformat    53. 32.100 / 53. 32.100
  libavdevice    53.  4.100 / 53.  4.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
Input #0, image2, from 'testpic.jpg':
  Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj422p, 753x1024 [SAR 72:72 DAR 753:1024], 25 tbr, 25 tbn, 25 tbc
Output #0, image2, to 'testpic-sized.jpg':
  Metadata:
    encoder         : Lavf53.32.100
    Stream #0:0: Video: mjpeg, yuvj422p, 753x1024, q=2-31, 200 kb/s, 90k tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg -> mjpeg)
Press [q] to stop, [?] for help
frame=    1 fps=  0 q=5.9 Lsize=       0kB time=00:00:00.04 bitrate=   0.0kbits/s   
video:77kB audio:0kB global headers:0kB muxing overhead -100.000000%