Parameter for A-SIFT detection

[xianggao1989]

Hi, In my opinion, the parameter '-t' in the file 'siftParam_sttings.txt' controls the number of the detected keypoints. However, the detected keypoints No. did not change a lot as expected when I changed the value of '-t'. Is there something wrong with my understanding of the parameter setting? Thanks a lot! Xiang Gao from NLPR, CASIA

[seravee08]

Hi Xiang,

Thanks for your email. The parameters in "siftParam_settings.txt" closely follow this document https://github.com/pitzer/SiftGPU/blob/master/doc/manual.pdf. https://mailtrack.io/trace/link/97aec3b18d2119b9a214562a9704627a29cafa8e?url=https%3A%2F%2Fgithub.com%2Fpitzer%2FSiftGPU%2Fblob%2Fmaster%2Fdoc%2Fmanual.pdf.&userId=622087&signature=5cdbbbfdc716698a Find the lookup table at bottom of this document and you will find the definition of the parameters.

In page 11 of the SIFT paper ( https://www.robots.ox.ac.uk/~vgg/research/affine/det_eval_files/lowe_ijcv2004.pdf https://mailtrack.io/trace/link/8ae4683c2bf6fd6d68de6ed8f54b2a4af60ab7f7?url=https%3A%2F%2Fwww.robots.ox.ac.uk%2F~vgg%2Fresearch%2Faffine%2Fdet_eval_files%2Flowe_ijcv2004.pdf&userId=622087&signature=0b44d424635e0e4f), t is the threshold deciding whether an extrema should be discarded. In other words, it does control the number of keypoints detected. Depending on the nature of the images, t could have major or minor impacts on the number of keypoints detected. This is an expected behavior.

Thanks and regards, Fan

On Thu, Sep 7, 2017 at 10:06 AM, xgao_nlpr notifications@github.com wrote:

Hi, In my opinion, the parameter '-t' in the file 'siftParam_sttings.txt' controls the number of the detected keypoints. However, the detected keypoints No. did not change a lot as expected when I changed the value of '-t'. Is there something wrong with my understanding of the parameter setting? Thanks a lot! Xiang Gao from NLPR, CASIA

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[xianggao1989]

Thanks for your reply!