1. A method for increasing object detection rates or object recognition rates by using a classifier, comprising the steps of: (a) the classifier acquiring a covariance matrix by using values of at least one channel of a combination of pixels amounting to a certain number less than the total number of pixels included in a local block having a smaller size than detection windows of respective image samples including positive image samples and hard negative image samples while moving the local block within the detection windows; and (b) the classifier acquiring a transform matrix w for transforming at least one feature vector x of an image as a subject to be classified, by using the covariance matrix, wherein the image is inputted to the classifier after acquiring the transform matrix w; and (c) the classifier acquiring at least one locally decorrelated channel feature (LDCF) value corresponding to the feature vector x by using the feature vector x and the transform matrix w, if the image is inputted to the classifier, wherein the LDCF value may be calculated as an inner product of the feature vector x and the transform matrix w.