Liquid level determination
Disclosed herein are a system and method for determining a liquid level in a container based on data extracted from a digital image of the container. An image capture apparatus captures an image of a container used to store liquid reagents used by analytical instruments to test patient samples. A controller receives the captured image and extracts an analysis region based on a container type and applies a gradient filter to the analysis region. A location of a minimum gradient value (i.e., a row index) is determined based on the air-to-liquid boundary of the liquid in the extracted analysis region. A volume module calculates the liquid level in the analysis region by dividing the row index by a length of a gradient column vector and compares the determined liquid level to a threshold analysis region fraction for the container type to determine whether to output an alert.
1. A system for determining a level of liquid in a container, the system comprising:
an image capture apparatus; and
a controller configured to:
receive a digital image of a container from the image capture apparatus, the container containing an unknown quantity of liquid;
extract an analysis region from the digital image;
calculate gradient values for different positions in the analysis region, wherein calculating gradient values comprises:
summing a plurality of row-wise pixel intensities in the analysis region,
computing a column-wise average of pixel intensities in the analysis region, and
for each row, computing a column-wise gradient value by computing an element wise subtraction of rows of the column-wise averages;
identify a minimum gradient value of the gradient values; and
determine a level of liquid in the container based on the position of the minimum gradient value in the analysis region.
2. The system of claim 1 , wherein the digital image is a color image and wherein the controller is further configured to convert the color image to grayscale.
3. The system of claim 1 , wherein the controller being configured to extract an analysis region from the digital image comprises the controller being configured to:
identify one or more visible indicia in the digital image;
query a data store for a container type associated with the identified visible indicia; and
identify a location of the analysis region in the digital image based on the container type.
4. The system of claim 1 , wherein the controller being configured to calculate gradient values for different positions in the analysis region comprises the controller being configured to:
apply a Sobel filter to pixels along a y-axis of the analysis region to extract a Sobel gradient; and
sum the extracted Sobel gradients along the x-axis of the analysis region.
5. The system of claim 1 , wherein the analysis region has a width of one pixel and wherein the controller being configured to calculate gradient values comprises the controller being configured to compute a row-wise intensity gradient of pixels along a y-axis of the analysis region.
6. The system of claim 1 , wherein the controller being configured to determine a level of liquid in the container comprises the controller being configured to compute a fraction of liquid in the analysis region by dividing a row index by a length of a gradient column vector in the analysis region.
7. The system of claim 1 , wherein the controller is further configured to:
compare the determined liquid level to a threshold level associated with a container type; and
responsive to determining that the liquid level is below the threshold level associated with the container type, outputting an alert to a display device.
8. The system of claim 1 , wherein the controller is further configured to determine a volume of liquid in the container based on the liquid level and a stored cross-sectional volume of the container.
9. The system of claim 1 , wherein the controller is further configured to:
compare the determined liquid level to a threshold level associated with a container type; and
responsive to determining that the liquid level is below the threshold level associated with the container type, switching an automated analyzer to a liquid-saving operation mode.
10. A computer-implemented method for determining a level of liquid in a container, the method comprising:
receiving a digital image of the container from an image capture apparatus, the container containing an unknown quantity of liquid;
extracting an analysis region from the digital image;
calculating gradient values for different positions in the analysis region, wherein calculating gradient values comprises:
summing a plurality of row-wise pixel intensities in the analysis region,
computing a column-wise average of pixel intensities in the analysis region, and
for each row, computing a column-wise gradient value by computing an element wise subtraction of rows of the column-wise averages;
identifying a minimum gradient value of the gradient values; and
determining a level of liquid in the container based on the position of the minimum gradient value in the analysis region.
11. The method of claim 10 , wherein the digital image is a color image and the method further comprises converting the color image to grayscale.
12. The method of claim 10 , wherein extracting an analysis region from the digital image comprises:
identifying one or more visible indicia in the digital image;
querying a data store for a container type associated with the identified visible indicia; and
identifying a location of the analysis region in the digital image based on the container type.
13. The method of claim 10 , wherein calculating gradient values for different positions in the analysis region comprises:
applying a Sobel filter to pixels along a y-axis of the analysis region to extract a Sobel gradient; and
summing the extracted Sobel gradients along the x-axis of the analysis region.
14. The method of claim 10 , wherein the analysis region has a width of one pixel and wherein calculating gradient values comprises computing a row-wise intensity gradient of pixels along a y-axis of the analysis region.
15. The method of claim 10 , wherein determining a level of liquid in the container comprises computing a fraction of liquid in the analysis region by dividing a row index by a length of a gradient column vector in the analysis region.
16. The method of claim 10 , further comprising:
comparing the determined liquid level to a threshold level associated with a container type; and
responsive to determining that the liquid level is below the threshold level associated with the container type, outputting an alert to a display device.
17. The method of claim 10 , further comprising determining a volume of liquid in the container based on the liquid level and a stored cross-sectional volume of the container.
18. The method of claim 10 , further comprising:
comparing the determined liquid level to a threshold level associated with a container type; and
responsive to determining that the liquid level is below the threshold level associated with the container type, switching an automated analyzer to a liquid-saving operation mode.