thresholdcv

Syntax

[computedthreshold, R] = thresholdcv(handle, threshold, max, type)

Inputs

handle

Handle of an image.

Type: integer

threshold

Real vector of [width height] representing the dimensions of R.

Type: vector

fx

Threshold value.

Type: scalar

max

Maximum value to use with type value of 8 or 16.

Type: scalar

type

Threshold type. Valid values are:

0

R(x,y) = max if handle(x,y) > threshold and 0 otherwise.

1

R(x,y) = 0 if handle(x,y) > threshold and max otherwise.

2

R(x,y) = threshold if handle(x,y) > threshold and handle(x,y) otherwise.

3

R(x,y) = handle(x,y) if handle(x,y) > threshold and 0 otherwise.

4

R(x,y) = 0 if handle(x,y) > threshold and handle(x,y) otherwise.

8

Uses Otsu algorithm for optimal threshold.

16

Uses Triangle algorithm for optimal threshold.

Type: integer

Outputs

computedthreshold

Computed threshold value.

Type: scalar

R

Handle of the resized image.

Type: integer

Example

Apply a threshold to an image:

handle = imreadcv('bird4.jpg', 0);
[computedthreshold, mask] = thresholdcv(handle, 10, 255, 0);

Figure 1. Input image

Figure 2. Mask

Apply a threshold to an image containing numbers written in grayscale equal to the number itself with threshold equals to zero and maximum value equals to 255 (white):

src = imreadcv('thresholdcv_fig1.png');
figure(1);
imshowcv(src);

thresh = 0;
maxValue = 255;

[computedthreshold, mask] = thresholdcv(src, thresh, maxValue, 0); %Binary threshold

figure(2);
imshowcv(mask);

Figure 3. Input image

Figure 4. Mask

Apply a threshold to the same image as described above containing numbers with threshold equals to 127, which removes all numbers less than or equal to 127:

src = imreadcv('thresholdcv_fig1.png');
figure(1);
imshowcv(src);

thresh = 127;
maxValue = 255;

[computedthreshold, mask] = thresholdcv(src, thresh, maxValue, 0); %Binary threshold

figure(2);
imshowcv(mask);

Figure 5. Mask

Apply a threshold as described in the previous example with a maximum value of 150, to set the value of the thresholded regions to 150:

src = imreadcv('thresholdcv_fig1.png');
figure(1);
imshowcv(src);

thresh = 127;
maxValue = 150;

[computedthreshold, mask] = thresholdcv(src, thresh, maxValue, 0); %Binary threshold

figure(2);
imshowcv(mask);

Figure 6. Mask

Apply a threshold to the same image as described above with threshold equals to zero and maximum value equals to 255 (white), but using the inverse binary thresholding:

src = imreadcv('thresholdcv_fig1.png');
figure(1);
imshowcv(src);

thresh = 0;
maxValue = 255;

[computedthreshold, mask] = thresholdcv(src, thresh, maxValue, 1); %Inverse binary threshold

figure(2);
imshowcv(mask);

Figure 7. Mask

Apply a threshold to the same image as described above with threshold equals to 150 and maximum value equals to 255 (white), using the truncate thresholding. All values above the threshold are set to the threshold value and all values below remain unchanged:

src = imreadcv('thresholdcv_fig1.png');
figure(1);
imshowcv(src);

thresh = 150;
maxValue = 255;

[computedthreshold, mask] = thresholdcv(src, thresh, maxValue, 2); %Inverse binary threshold

figure(2);
imshowcv(mask);

Figure 8. Mask