android - Perspective correction of imageview -


i'm working on app needs apply perspective distortion correction photo taken phone's camera. once photo taken, idea show on imageview , let user mark 4 corners of document (a card, sheet of paper, etc.) , apply correction based on points. example of im trying achieve:

http://1.bp.blogspot.com/-ro9hnipj52e/tkom0ktleni/aaaaaaaaabq/c2r5vrgmc_w/s640/s4.jpg

any ideas on how on android?

what want goes under various names of art, "corner-pin" being 1 commonly used in visual effects industry. need proceed in 2 steps:

  1. compute mapping the desired, rectified image, original, distorted, image
  2. actually warp original image according mapping computed in (1).

the 4 (non-collinear, perspective-distorted) corners of original image, , 4 corners of target (undistorted) image, define mapping. mapping called "homography" - read pointed wikipedia page details. once mapping known, warping @ step (2) can computed interpolation: every pixel in target image, find corresponding pixel in original image. typically not @ integer coordinates, interpolate color neighbors. various interpolation schemes used, common ones being nearest-neighbor, bilinear , bicubic (in increasing order of smoothness in results).

for android, i'd recommend installing opencv sdk , , use geometry transformation routines (getperspectivetransform , warpperspective 2 steps above).


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