At its present stage

pencil drawing using a computer cannot approximate reality primarily because tone in real penciling has more obvious characteristics in dark

grey

and bright layers' changing than in a greyscale image. To address this problem

a novel pencil drawing automatic generation method is proposed. The new method replaces traditional gradient image method to combine a LAB space color difference image and a texture image as features for outer outline extraction. It also allows thetexture's constant hue to change in the rendering process. An arctangent hue differentiation model is likewise proposed to reflect the hue layered effect.The core idea

based on the dark

grey and bright layers' pixelratio

is to adjust the pixel grey value to achieve layering tones. The new method avoids noise impact and displays detailsbetter. It not only resolves the sudden color change in direct stratification but also achieves integration between brightness stratification and continuous huechanges. The final effect shows that the new algorithm has two advantages over other algorithms. First

the outline is more continuous and clear. Second

the effect of texture can achieveboth consistency and layering

which cannot be achieved by other algorithms. The proposedalgorithm can be applied to either colorful or grey images of various resolutions; the higher the resolution is

the better the effect is.