1 /** 2 * @desc 二次线性插值公式 3 * P0 P2 4 * P1 P3 5 * 6 * pm0=(1-u)*(1-v); 7 * pm1=v*(1-u); 8 * pm2=u*(1-v); 9 * pm3=u*v; 10 * 11 * dst = P0*pm0 + P1*pm1 + P2*pm2 + P3*pm3; 12 * @param pline1 原图像P0 P2 13 * @param pline2 原图像P1 P3 14 * @param channels 图像通道数，1=灰阶、3=RGB888彩色 15 * @param u 16 * @param v 17 * @return 目标像素值 18 * **/ 19 unsigned char linearInterpolation(unsigned char* pline1, unsigned char* pline2, int channels,int u, int v){ 20 int pm3 = u * v; 21 int pm2 = (u << 8) - pm3; 22 int pm1 = (v << 8) - pm3; 23 int pm0 = (1 << 16) - pm1 - pm2 - pm3; 24 25 unsigned char result = (unsigned char)(((pm0*pline1[0] + pm2 * pline1[channels] + pm1 * pline2[0] + pm3* pline2[channels]) >> 16)&0xff); 26 27 return result; 28 } 29 30 /** 31 * @desc 二次线性插值图像缩放 32 * @param psrc 原图像 33 * @param sw 原图像宽度 34 * @param sh 原图像高度 35 * @param channels 图像通道数，1=灰阶、3=RGB888彩色 36 * @param pdst 缩放后图像 37 * @param dw 缩放后图像宽度 38 * @param dh 缩放后图像高度 39 * **/ 40 void zoomImg(unsigned char *psrc, int sw, int sh,int channels, unsigned char *pdst, int dw, int dh) 41 { 42 if (!psrc || !pdst) return; 43 if (sw <= 0 || sh <= 0 || dw <= 0 || dh <= 0) return; 44 if (channels != 1 && channels != 3) return; 45 46 unsigned char *p = psrc,*q = pdst,*pt; 47 int srcBytesPerLine = sw * channels,dstBytesPerLine = dw * channels; 48 int srcy_16 = 0, v_8 = 0, srcx_16 = 0; 49 int stepw = (((sw - 1) << 16) / dw +1); 50 int steph = ((sh - 1) << 16) / dh + 1; 51 int stepc = ((channels - 1) << 16)/channels + 1; 52 int i, j, m; 53 54 srcy_16 = 0; 55 for (j = 0; j < dh; j++) 56 { 57 v_8 = (srcy_16 & 0xFFFF) >> 8; 58 p = psrc + srcBytesPerLine * (srcy_16 >> 16); 59 srcx_16 = 0; 60 for (i = 0; i < dstBytesPerLine; i+=channels) 61 { 62 pt = &p[(srcx_16>>16)*channels]; 63 64 for (m = 0; m < channels; m++) { 65 q[i+m] = linearInterpolation(&pt[m], &pt[m] + srcBytesPerLine, channels, (srcx_16 & 0xFFFF) >> 8, v_8); 66 } 67 68 srcx_16 += stepw; 69 } 70 srcy_16 += steph; 71 72 q += dstBytesPerLine; 73 } 74 }