Not necessarily, but the best choice depends on which details you would like to emphasize. I don't know the context of the sentence, so a few options are below to hopefully cover this specific use case (there could well be a couple suitable stylistic approaches):
a.) "...there exist sufficient white pixels on the edges of the pallet car that reside on a straight line."
--> This implies that it's important that these pixels reside on a straight line vs. others on the edges of the pallet. Stylistically it's a bit wordy.
b.) "...there exist sufficient white pixels on the edges of the pallet car, which reside on a straight line."
--> This implies that there exist sufficient pixels on the edges of the pallet car, and they happen to also be in a straight line (for the reader's reference).
c.) "...there exist sufficient white pixels residing/that reside on a straight line on the edges of the pallet car."
--> Similar to a.) and probably stylistically cleaner; implies that it's important that these pixels reside on a straight line as a defining characteristic of these pixels
d.) "...there exist sufficient white pixels, residing on a straight line on the edges of the pallet car."
--> Similar to f.) implies that there are sufficient white pixels in general, and that you can see them residing on a straight line on the edges of the pallet car.
d.) "...there exist sufficient white pixels, which reside on a straight line, on the edges of the pallet car."
--> Similar to b.); emphasizes that there are sufficient white pixels on the edges of the pallet car, and that they area also in a straight line (for reference).
f.) "...there exist sufficient white pixels, which reside on a straight line on the edges of the pallet car."
--> Implies in that there are sufficient white pixels (in general)and that they happen to both reside on a straight line and be on the edges of the pallet car.