What is the dot-product of two images?

StridingDragon
Posts: 32
Joined: Fri Aug 02, 2019 11:59 pm

What is the dot-product of two images?

Postby StridingDragon » Thu Sep 09, 2021 5:53 pm

While looking through the ESP32 DSP documentation (https://docs.espressif.com/projects/esp ... marks.html) I stumbled across functions that reportedly create the "dotproduct of two images"—no other information is provided.

I have never heard of a dot-product of two images in all my years of graphics programming—but it may be a signal processing-specific expression. I have trouble wrapping my head around the term because images are 2D arrays of pixels and the dot-product is a vector operation. I just don't see how the two things are in any way related or what result the operation would yield.

Can anyone tell me what the dot-product of two images is and what it is used for?

Craige Hales
Posts: 5
Joined: Tue Sep 07, 2021 12:07 pm

Re: What is the dot-product of two images?

Postby Craige Hales » Sat Sep 11, 2021 12:49 pm

https://github.com/espressif/esp-dsp/bl ... _dotprod.h
is the only info I found. It might be the sum of the pixel-by-pixel product.
If the image pixels are signed, between -1 and 1, the result might be a correlation between the images...negative total if most pixels had opposite sign values, positive total if most had same sign values.
I'm guessing. Never seen it before either.
Craige

StridingDragon
Posts: 32
Joined: Fri Aug 02, 2019 11:59 pm

Re: What is the dot-product of two images?

Postby StridingDragon » Wed Sep 15, 2021 5:59 pm

Too bad no one seems to have an answer for this. I can see the implementation of it (https://github.com/espressif/esp-dsp/tr ... es/dotprod) and all it does is multiply pixels with each other and summing the products up as the return value. Not sure for what purpose this operation could be useful.

tommeyers
Posts: 152
Joined: Tue Apr 17, 2018 1:51 pm
Location: Santiago, Dominican Republic

Re: What is the dot-product of two images?

Postby tommeyers » Wed Sep 15, 2021 9:17 pm

Investigate SVD

http://blog.kleinproject.org/?p=588

Please tell us what you think.

Tom
IT Professional, Maker
Santiago, Dominican Republic

StridingDragon
Posts: 32
Joined: Fri Aug 02, 2019 11:59 pm

Re: What is the dot-product of two images?

Postby StridingDragon » Thu Sep 16, 2021 5:30 pm

Interesting. Thanks, Tom. This is exciting stuff. I had not heard of SVD before, but it sounds really impressive.

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