{"id":75,"date":"2009-06-18T14:06:49","date_gmt":"2009-06-18T04:06:49","guid":{"rendered":"http:\/\/www.computer-vision-software.com\/blog\/?p=75"},"modified":"2009-11-30T13:11:18","modified_gmt":"2009-11-30T03:11:18","slug":"fastfurious-face-detection-with-opencv","status":"publish","type":"post","link":"http:\/\/www.computer-vision-software.com\/blog\/2009\/06\/fastfurious-face-detection-with-opencv\/","title":{"rendered":"Fast & Furious face detection with OpenCV"},"content":{"rendered":"

In OpenCV\/Samples there is\u00a0 facedetect program.\u00a0 This program can detect\u00a0 faces on images and video.\u00a0 It’s very fun, but its speed leaves much to be desired =(.\u00a0 Of course\u00a0 with OpenMP,\u00a0 it works\u00a0 faster; on Intel Core Duo 2.7GHZ, it works fast;\u00a0 but will it work fast on ARM? I have big doubts.\u00a0 I compiled facedetect without OpenMP and on average it takes 600 ms for 640×480 resolution to find one face. \u00a0 I wanted to find out, if it’s possible to improve this time by software means or not…\u00a0 After some investigations, code refactoring and improvements, facedetect started to work 2.5 time faster<\/strong>, even on ARM.\u00a0 Of course, without big quality loss<\/strong> =)<\/p>\n

<\/p>\n

I started investigation with profiling cvHaarDetectObjects on 640×480 image.\u00a0 Function cvRunHaarClassifierCascade tooks 70% of computation time<\/span>.\u00a0 But cvRunHaarClassifierCascade is not so heavy, why it takes so much time? Scanning 20×20 window is moved on X-direction and Y-direction and Scale-direction and on each scanning window, cvRunHaarClassifierCascade is called.\u00a0 Totally we have 160000<\/strong> calls!<\/p>\n

So to reduce time, we need optimize this triple cycle<\/span>.\u00a0 I know several ways:<\/p>\n

    \n
  1. change parameters in cvHaarDetectObjects function.\u00a0 Sometimes, it really helps, but let’s resort to such shamanism another time.\u00a0\u00a0 I used “default” parameters: 1.1 scale factor, 20×20 window<\/em>.<\/li>\n
  2. use fixed point in algorithm.\u00a0 We did it here<\/a><\/li>\n
  3. optimize OpenCV default frontal face cascade.\u00a0 Cascade generation<\/a> takes much time and who knows, will it be good or not =)<\/li>\n
  4. somehow reduce number of cvRunHaarClassifierCascade calls.\u00a0 Image contains only several real faces, not 160000 – so all this makes sence.<\/li>\n<\/ol>\n

    We have researched a lot of approaches and combination of ways above and got the result (Intel Core Duo 2.7GHZ):<\/p>\n

    \"2\"<\/p>\n

    \n\n\n<\/col>\n<\/col>\n<\/colgroup>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
    <\/td>\nOriginal face detect<\/td>\nFast face detect<\/td>\n<\/tr>\n
    <\/td>\nColorFERET
    \nfrontal<\/td>\n    		LabeledFaces
    \nInTheWild<\/td>\n    		NoFaces
    \n(Negative)<\/td>\n    		ColorFERET
    \nfrontal<\/td>\n    		LabeledFaces
    \nInTheWild<\/td>\n    		NoFaces
    \n(Negative)<\/td>\n<\/tr>\n
    <\/td>\n512×768<\/td>\n250×250<\/td>\nup to
    \n1280×1024<\/td>\n    		512×768<\/td>\n250×250<\/td>\nup to
    \n1280×1024<\/td>\n<\/tr>\n
    <\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
    Total<\/td>\n5444<\/td>\n1872<\/td>\n1748<\/td>\n5276<\/td>\n1872<\/td>\n1748<\/td>\n<\/tr>\n
    <\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
    Fount<\/td>\n5420<\/td>\n1765<\/td>\n<\/td>\n5191<\/td>\n1685<\/td>\n<\/td>\n<\/tr>\n
    Hit rate<\/td>\n99,6%<\/td>\n94,3%<\/td>\n<\/td>\n98,4%<\/td>\n90,0%<\/td>\n<\/td>\n<\/tr>\n
    FP (incorrect found)<\/td>\n57<\/td>\n12<\/td>\n37<\/td>\n18<\/td>\n10<\/td>\n13<\/td>\n<\/tr>\n
    False alarm rate<\/td>\n<\/td>\n<\/td>\n2,1%<\/td>\n<\/td>\n<\/td>\n0,7%<\/td>\n<\/tr>\n
    FN (not found)<\/td>\n23<\/td>\n107<\/td>\n<\/td>\n85<\/td>\n187<\/td>\n<\/td>\n<\/tr>\n
    <\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
    Average time, ms<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
    not found<\/td>\n623,98<\/td>\n85,43<\/td>\n775,23<\/td>\n139,07<\/td>\n39,48<\/td>\n287,98<\/td>\n<\/tr>\n
    one face found<\/td>\n629,53<\/td>\n87,07<\/td>\n1053,49<\/td>\n248,26<\/td>\n42,99<\/td>\n455,31<\/td>\n<\/tr>\n
    two or more face found<\/td>\n632,32<\/td>\n88,04<\/td>\n<\/td>\n245,12<\/td>\n43,39<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

    In OpenCV\/Samples there is\u00a0 facedetect program.\u00a0 This program can detect\u00a0 faces on images and video.\u00a0 It’s very fun, but its speed leaves much to be desired =(.\u00a0 Of course\u00a0 with OpenMP,\u00a0 it works\u00a0 faster; on Intel Core Duo 2.7GHZ, it works fast;\u00a0 but will it work fast on ARM? I have big doubts.\u00a0 I compiled […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[84],"tags":[7,29,31,6,28,30],"class_list":["post-75","post","type-post","status-publish","format-standard","hentry","category-opencv","tag-arm","tag-face-detection","tag-haar","tag-opencv","tag-performance","tag-viola-jones"],"_links":{"self":[{"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/posts\/75","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/comments?post=75"}],"version-history":[{"count":0,"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/posts\/75\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/media?parent=75"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/categories?post=75"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.computer-vision-software.com\/blog\/wp-json\/wp\/v2\/tags?post=75"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}