Image processing device and method for color balancing

An imaging system comprising:

• a first camera;
• a second camera;
• and
• an image processing device comprising one or more processors adapted to:
• determine a global gain vector (t) comprising at least one gain factor (ân) of the first image and at least one gain factor (ân+1) of the second image by minimizing a pre-determined cost function based upon reference pixel values of the first image and reference pixel values of the second image, wherein the first and second image reference pixels depict a shared color scene of the first and second images;
• perform a color balancing of the first image based upon the at least one gain factor (ân) of the first image;
• and
• perform a color balancing of the second image based upon the at least one gain factor (ân+1) of the second image,
• wherein minimizing the pre-determined cost function comprises minimizing
• J′=[yj(1) yj(2)][a(2) −a(1)]T,
• wherein J′ is the predetermined cost function T is a transpose j is a pixel number yj(1) is a value of pixel number j measured by the first camera, y1(2) is a value of pixel number j measured by the second camera, a(1) is a gain factor by which a reference color value of the pixel j has to be multiplied to equal yj(1) and a(2) is a gain factor by which the reference color value of the pixel j has to be multiplied to equal yj(2).

An image processing method for performing a color balancing of at least a first image recorded by a first camera and a second image recorded by a second camera,

• the method comprising:
• determining a global gain vector (t) comprising at least one gain factor (ân) of the first image and at least one gain factor (ân+1) of the second image by minimizing a pre-determined cost function based upon reference pixel values of the first image and reference pixel values of the second image, wherein the first and second image reference pixels depict a shared color scene of the first and second images;
• performing a color balancing of the first image based upon the at least one gain factor (ân) of the first image;
• and
• performing a color balancing of the second image based upon the at least one gain factor (ân+1) of the second image,
• wherein minimizing the pre-determined cost function comprises minimizing
• J′=[yj(1) yj(2)][a(2) −a(1)]T,
• wherein J′ is the predetermined cost function, T is a transpose, j is a pixel number, yj(1) is a value of pixel number j measured by the first camera y1(2) is a value of pixel number j measured by the second camera, a(1) is a gain factor by which a reference color value of the pixel j has to be multiplied to equal yj(1) and a(2) is a gain factor by which the reference color value of the pixel j has to be multiplied to equal yj(2).

A non-transitory computer readable medium comprising a program code for performing a color balancing of at least a first image recorded by a first camera and a second image recorded by a second camera when the program code runs on a computer, the computer is configured to perform steps comprising:

• determining a global gain vector (t) comprising at least one gain factor (ân) of the first image and at least one gain factor (ân+1) of the second image by minimizing a pre-determined cost function based upon reference pixel values of the first image and reference pixel values of the second image, wherein the first and second image reference pixels depict a shared color scene of the first and second images;
• performing a color balancing of the first image based upon the at least one gain factor (ân) of the first image;
• and
• performing a color balancing of the second image based upon the at least one gain factor (ân+1) of the second image,
• wherein minimizing the pre-determined cost function comprises minimizing
• J′=[yj(1) yj(2)][a(2) −a(1)]T,
• wherein J′ is the predetermined cost function, T is a transpose, j is a pixel number, yj(1) is a value of pixel number j measured by the first camera, y1(2) is a value of pixel number j measured by the second camera, a(1) is a gain factor by which a reference color value of the pixel j has to be multiplied to equal yj(1), and a(2) is a gain factor by which the reference color value of the pixel j has to be multiplied to equal yj(2).