Color layout descriptor

[1] The feature extraction process consists of two parts: grid based representative color selection and discrete cosine transform with quantization.

The CLD captures the spatial layout of the representative colors on a grid superimposed on a region or image.

In the image partitioning stage, the input picture (on RGB color space) is divided into 64 blocks to guarantee the invariance to resolution or scale.

The inputs and outputs of this step are summarized in the following table: After the image partitioning stage, a single representative color is selected from each block.

The inputs and outputs of this stage are summarized in the next table: Once the tiny image icon is obtained, the color space conversion between RGB and YCbCr is applied.

The inputs and outputs of this stage are summarized in the next table: A zigzag scanning is performed with these three sets of 64 DCT coefficients, following the schema presented in the figure.