1. An image signal processing system comprising: an image sensor configured to receive image data; an image processing pipeline configured to detect and correct a defective image pixel by: receiving an input pixel of the image data acquired using the image sensor; identifying a set of neighboring pixels having the same color component as the input pixel; removing two neighboring pixels from the set of neighboring pixels thereby generating a modified set of neighboring pixels, wherein the two neighboring pixels correspond to a maximum pixel value and a minimum pixel value of the set of neighboring pixels; determining a gradient for each neighboring pixel in the modified set of neighboring pixels; and determining whether the input pixel comprises a speckle based at least in part on the gradient for each neighboring pixel in the modified set of neighboring pixels, wherein determining whether the input pixel comprises the speckle comprises: determining an average pixel value based at least in part on each pixel value in the modified set of neighboring pixels; determining an average gradient value based at least in part on a pixel value that corresponds to the input pixel and the average pixel value; determining a despeckle threshold value by: determining at least two brightness levels of a plurality of brightness levels, wherein the at least two brightness levels comprise a brightness level above and below a brightness value that corresponds to the average pixel value; determining a first filter coefficient based at least in part on a first data array, the at least two brightness levels, at least two brightness values associated with the at least two brightness levels, and the average pixel value, wherein the first data array comprises a first plurality of threshold values indexed with respect to a color component of the input pixel and a brightness level of the plurality of brightness levels that corresponds to the average pixel value; determining a second filter coefficient based at least in part on a second data array, the at least two brightness levels, the at least two brightness values associated with the at least two brightness levels, and the average pixel value, wherein the second data array comprises a second plurality of threshold values indexed with respect to the color component of the input pixel and the brightness level of the plurality of brightness levels that corresponds to the average pixel value; and interpolating the first filter coefficient and the second filter coefficient; comparing the average gradient value to the despeckle threshold value; and identifying the input pixel as comprising the speckle if the average gradient value is greater than the despeckle threshold value.