And the context. For example, self-driving cars need to account for "Pizza Stop" restaurant signage, placards stuck to telephone poles that say things like "Stop Cancer", stop signs retracted into the sides of school buses, signs with additional instructions like "Stop when lights flashing", road workers with handheld stop signs, and the unconventional stop signs you see in parking lots.
You can probably get pretty far by checking the proximity to the road, height, dimensions, orientation, what it's mounted on, and if the sign incorporates any other text. But you can't just scan some pixels for "red octagon with STOP on it".
And the context. For example, self-driving cars need to account for "Pizza Stop" restaurant signage, placards stuck to telephone poles that say things like "Stop Cancer", stop signs retracted into the sides of school buses, signs with additional instructions like "Stop when lights flashing", road workers with handheld stop signs, and the unconventional stop signs you see in parking lots.
You can probably get pretty far by checking the proximity to the road, height, dimensions, orientation, what it's mounted on, and if the sign incorporates any other text. But you can't just scan some pixels for "red octagon with STOP on it".