基于频率分级的指纹图像压缩算法

指纹图像是由黑白相间的脊线、谷线排列在一起而构成的特殊灰度图像,反复出现的反差边缘、周围的背景区域使得指纹图像具备低、中、高三种不同的频率成分,本文利用小波包变换和频谱分析提出了一种基于频率分级的指纹图像压缩算法,对包含能量最多的低频子图像,采用无损差分脉冲编码(DPCM)算法;对包含能量较少的中频子图像,采用嵌入式小波零数编码(EZW)算法;对包含能量最少的高频子图像,采用集合分裂嵌入块编码(SPECK)算法。仿真实验表明,本算法在保证重建质量的前提下,压缩比平均提高了21.4%左右,逼真度平均提高了6.25%左右。

Fingerprint Image Compression Algorithm Based on Graded Frequency

Fingerprint image is a special kind of gray image which consists with ridge and valley lines in black and white. The fingerprint image has different frequency component, low, medium and high frequency. The fingerprint image compression algorithm based on graded frequency is proposed. The low frequency sub-image, which contains the most energy, is encoded by lossless Differential Pulse Code Modulation (DPCM). The medium frequency sub-image, which contains less energy, is encoded by Embedded Zero-tree Wavelet (EZW). The high frequency sub-image, which contains the least energy, is encoded by Set Partitioning Embedded Block Coder (SPECK). The experimental result indicates, compared with the other image encoding method, the presented algorithm improves the compression ratio by about 21.4 percent and fidelity by about 6.25 percent in conditions of ensuring reconstruction quality.