Gaussian blur approximation suitable for GPU

An image processing software application stored on a computer-readable medium comprising instructions for causing one or more programmable control devices to:

• identify an image, the image having an original size;
• specify a blur-value indicating an amount to blur the image;
• determine a number of times to down-sample the image with a truncated Gaussian filter having a variance, based on the blur-value;
• down-sample the image the determined number of times with the truncated Gaussian filter;
• and
• up-sample the down-sampled image to return it to approximately its original size.

A method to blur an image, comprising:

• obtaining an image having an original size;
• receiving a blur-value indicating an amount to blur the image;
• determining a number of times to down-sample the image with a first truncated Gaussian filter having a first variance, based on the blur-value;
• determining a second truncated Gaussian filter based on a second variance, the second variance being equal to the difference between the blur-value and the variance resulting from down-sampling the image the determined number of times;
• down-sampling the image the determined number of times with the first truncated Gaussian filter to generate a first intermediate image;
• convolving the first intermediate image with the second truncated Gaussian filter to generate a second intermediate image;
• and
• up-sampling the second intermediate image to return it to a size approximately equal to the size of the image.

An image processing software application stored on a computer-readable medium comprising instructions for causing one or more programmable control devices to:

• obtain an image;
• receive a blur-value indicating an amount to blur the image;
• determine a number of times to down-sample the image with a first truncated Gaussian filter having a first variance, based on the blur-value;
• determine a second truncated Gaussian filter based on a second variance, the second variance being equal to the difference between the blur-value and the variance resulting from down-sampling the image the determined number of times;
• down-sample the image the determined number of times with the first truncated Gaussian filter to generate a first intermediate image;
• convolve the first intermediate image with the second truncated Gaussian filter to generate a second intermediate image;
• and
• up-sample the second intermediate image to return it to a size approximately equal to the size of the image.