Vision information

[Nando88]

I'm not very experienced in labview, andI'm using OCR with the vision assistant.

I would like to know if someone could tell me what is threshold, and why do I have to train the vision assistant with characters the database already has, when I move the object farther away from the camera?

Thanks in advance!

[Nando88]

why is working in an environment with constant illumination, necessary for the application to work correctly?

[muks]

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@Nando88 wrote:

why is working in an environment with constant illumination, necessary for the application to work correctly?

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Ofcourse. Constant illumination is neccasary for all image processing functions to give you a repeatable consistent result. Regarding your OCR question You will ned to train the characters and store it . Post an image if you have difficulty

[Nando88]

Can you answer the first 2 questions, please?

[muks]

This is from context help

1. If you manually set the threshold values, and OCR/OCV cannot detect characters in the region you specified, the training process does not create the character set file correctly. For example, if you select Fixed Range from the Mode control, and you select a Max value that is too low, OCR/OCV cannot correctly detect the characters in the region of interest.
2. Select a threshold type from the Mode control.

   When you select Linear or Nonlinear, you must set # of Blocks to at least the number of objects in the region of interest. If you selected Fixed Range in Type, use Min and Max or the slider at the bottom of the histogram to determine the threshold value. If you selected Computed, Linear, or Nonlinear in Type, use Characters to indicate the character color in the image. Light on Dark indicates that the image contains light characters on a dark background. Dark on Light indicates that the image contains dark characters on a light background.

Moving object farther away is expected to create inconsistensies. If you can post an image i will try to work something

[Nando88]

I got my app working, the thing is that I still do not understand what the meaning of threshold is.
Could you please tell me what it is?
Thanks in advance.

[muks · Accepted solution]

An 8 bit gray scale image will be having values of 0 to 255. 0 being black and 255 corresponds to white. By threshold you are setting a range whose pixel values you want to use it for further processing. If you want to just get bright and near white pixel values then your thresold values will be something like min - 200 and max 255.

[muks]

Is this connected by any chance? Did you try the sampling thing before OCR.

[Nando88]

What sampling thing?

[muks]

Did you not see the vis attached in this post