Question

似乎双三次插值仅适用于高档。我试过这些功能： http://jsperf.com/pixel-interpolation/4和 http://www.reddit.com/r/javascript/comments/jxa8x/bicubic_interpolation/

我也尝试过Gernot Hoffmann的书“图像变形插值”中的双立方插值算法。

但是使用上述方法缩小后的所有图像看起来都是由近邻插值的。

也许我错了什么？

我也注意到在Photoshop中有两个单独的双三次插值选项：双立方平滑器（用于高级）和双立方锐化器（用于缩小）。

那么也许有人知道用于缩减尺度的双三次插值算法？

Answer 1

我刚写了一个双三次插入算法... 我运作良好。在运行之前，根据图像更改一些值;

ROW＆amp;列

#define ROW 218 //change 218 to your image's horizantol pixels #define COLUMN 329` //change 329 to your image's vertical pixels

ZOOM_RATE＆amp; ZOOM_NUM

ZOOM_RATE是图片调整大小的速度，如果你想要将其公开，然后将其设为“2”

ZOOM_NUM = 1 / ZOOM_RATE - ＆gt; ZOOM_NUM在ZOOM_RATE
上等于1
图片的名称和扩展名
int main（）函数更改
中的

readPpm("irfan.ppm"); //change irfan to your image's name

这里是源代码:(此代码也有双线性插件，所以你可以比较你的结果）

#include <stdio.h> #include <stdlib.h> #include <iostream> #include <fstream> #include <string.h> #include <string> #include <sstream> #include <string.h> #include <vector> #include <math.h> using namespace std; #define ROW 218 #define COLUMN 329 #define ZOOM_RATE 2 #define ZOOM_NUM 1/2 struct POINT { // Declare POINT structure int x; // Define members x and y int y; int renk; } ; // Variable spot has // values x = 20, y = 40 typedef struct POINT coordinate; // Variable there has POINT type int int_arr[ROW][COLUMN*3]; int int_arr_simple[ROW][COLUMN]; int zoom_photo[(int)(ROW*ZOOM_RATE)][(int)(COLUMN*ZOOM_RATE)]; int zoom_photo_bicubic[(int)(ROW*ZOOM_RATE)][(int)(COLUMN*ZOOM_RATE)]; string filetype; string comment; string size; string colorrange; int line_find(int ,int,int,int,float); void save2Ppm(string filename,int pixel[ROW][COLUMN*3],int size); void save2Pgm(string filename,int pixel[ROW][COLUMN],int size); void save2Pgm_zoom(string filename,int pixel[ROW*ZOOM_RATE][COLUMN*ZOOM_RATE],int size); void readPpm(string); void zooming(); void zooming_bilinear(); void zooming_bicubic(); int bicubic_function(float x_cor,float y_cor); void save2Pgm_zoom(string filename,int pixel[ROW*ZOOM_RATE][COLUMN*ZOOM_RATE],int size){ ofstream Picture; Picture.open(filename); Picture<<"P2\n#"<<filename<<"\n"<<(int)(COLUMN*ZOOM_RATE)<<" "<<(int)(ROW*ZOOM_RATE)<<"\n"<<size<<"\n"; for(int i=0 ; i<ROW*ZOOM_RATE ; i++) { for(int j=0; j<COLUMN*ZOOM_RATE; j++){ Picture<<pixel[i][j]<<" "; } } Picture.close(); } void zooming(){ for(int i=0;i<ROW*ZOOM_RATE;i++){ for(int j=0;j<COLUMN*ZOOM_RATE;j++){ zoom_photo[i][j]=int_arr_simple[i*ZOOM_NUM][j*ZOOM_NUM]; } } } void save2Pgm(string filename,int pixel[ROW][COLUMN],int size){ ofstream Picture; Picture.open(filename); Picture<<"P2\n#"<<filename<<"\n"<<COLUMN<<" "<<ROW<<"\n"<<size<<"\n"; for(int i=0 ; i<ROW ; i++) { for(int j=0; j<COLUMN; j++){ Picture<<pixel[i][j]<<" "; } } Picture.close(); } void save2Ppm(string filename,int pixel[ROW][COLUMN*3],int size){ ofstream Picture; Picture.open(filename); Picture<<"P3\n#"<<filename<<"\n"<<COLUMN<<" "<<ROW<<"\n"<<size<<"\n"; for(int i=0 ; i<ROW ; i++) { for(int j=0; j<COLUMN*3; j++){ Picture<<pixel[i][j]<<" "; } } Picture.close(); } void readPpm(string filename){ ifstream Picture(filename); //Picture.open(filename); char take[10000]; if(!Picture) printf("FILE NOT OPEN!!!!!!\n"); else { Picture.getline( take, 10000 ); for(int i = 0; take[i] != 0; i++) filetype += take[i]; Picture.getline( take, 10000 ); for(int i = 0; take[i] != 0; i++) comment += take[i]; Picture.getline( take, 10000 ); for(int i = 0; take[i] != 0; i++) size += take[i]; Picture.getline( take, 10000 ); for(int i = 0; take[i] != 0; i++) colorrange += take[i]; Picture.getline( take, 10000 ,' '); int_arr[0][0]=atoi(take); for(int i=1,j=0,t=0;i<ROW*COLUMN*3;i++){ Picture.getline( take, 10000 ,' '); t=i%(COLUMN*3); if(i%(COLUMN*3)==0) j++; int_arr[j][t]=atoi(take); int_arr_simple[j][t/3]=int_arr[j][t]; } Picture.close(); } } void zooming_bilinear(){ double x,y; double result_x,result_y,result; double x_1,x1; double y_1,y1; for(int i=0;i<ROW*ZOOM_RATE;i++){ for(int j=0;j<COLUMN*ZOOM_RATE;j++){ y=(double)ZOOM_NUM*i; x=(double)ZOOM_NUM*j; x_1 = (int)x; y_1 = (int)y; x1 = (int)(x+1); y1 = (int)(y+1); result_x=(double)(x1-x)*int_arr_simple[(int)y_1][(int)x_1]/(double)(x1-x_1) + (double)(x-x_1)*int_arr_simple[(int)y_1][(int)x1]/(double)(x1-x_1); result_y=(double)(x1-x)*int_arr_simple[(int)y1][(int)x_1] /(double)(x1-x_1) + (double)(x-x_1)*int_arr_simple[(int)y1][(int)x_1]/(double)(x1-x_1); result=(double)(y1-y)*result_x/(double)(y1-y_1) + (double)(y-y_1)*result_y /(double)(y1-y_1 ); zoom_photo[i][j]=result; } } } void zooming_bicubic(){ double x,y; double result_x,result_y,result; double x_1,x1; double y_1,y1; //zoom 16 pixel arasında olduğu için verileri atmaya 2,2 den başlıyor ve 2 birim önce bitiyor... for(int i=1;i<ROW*ZOOM_RATE-1;i++){ for(int j=1;j<COLUMN*ZOOM_RATE-1;j++){ zoom_photo_bicubic[i][j]=bicubic_function((float)ZOOM_NUM*j,(float)ZOOM_NUM*i); } } } int bicubic_function(float x_cor,float y_cor){//bicubic yöntemle renk döndürmek için kullanılan fonksiyon coordinate nokta[4][4]; int result;//en sonunda rengi döndüren variable nokta[0][0].x=(int)y_cor-1; nokta[0][0].y=(int)x_cor-1; nokta[0][1].x=(int)y_cor-1; nokta[0][1].y=(int)x_cor; nokta[0][2].x=(int)y_cor-1; nokta[0][2].y=(int)x_cor+1; nokta[0][3].x=(int)y_cor-1; nokta[0][3].y=(int)x_cor+2; nokta[1][0].x=(int)y_cor; nokta[1][0].y=(int)x_cor-1; nokta[1][1].x=(int)y_cor; nokta[1][1].y=(int)x_cor; nokta[1][2].x=(int)y_cor; nokta[1][2].y=(int)x_cor+1; nokta[1][3].x=(int)y_cor; nokta[1][3].y=(int)x_cor+2; nokta[2][0].x=(int)y_cor+1; nokta[2][0].y=(int)x_cor-1; nokta[2][1].x=(int)y_cor+1; nokta[2][1].y=(int)x_cor; nokta[2][2].x=(int)y_cor+1; nokta[2][2].y=(int)x_cor+1; nokta[2][3].x=(int)y_cor+1; nokta[2][3].y=(int)x_cor+2; nokta[3][0].x=(int)y_cor+2; nokta[3][0].y=(int)x_cor-1; nokta[3][1].x=(int)y_cor+2; nokta[3][1].y=(int)x_cor; nokta[3][2].x=(int)y_cor+2; nokta[3][2].y=(int)x_cor+1; nokta[3][3].x=(int)y_cor+2; nokta[3][3].y=(int)x_cor+2; float xline_1,xline_2,xline_3,xline_4; int P00,P01,P02,P03; P00=int_arr_simple[nokta[0][0].x][nokta[0][0].y-1]; P01=int_arr_simple[nokta[0][1].x][nokta[0][1].y-1]; P02=int_arr_simple[nokta[0][2].x][nokta[0][2].y-1]; P03=int_arr_simple[nokta[0][3].x][nokta[0][3].y-1]; int P10,P11,P12,P13; P10=int_arr_simple[nokta[1][0].x][nokta[1][0].y-1]; P11=int_arr_simple[nokta[1][1].x][nokta[1][1].y-1]; P12=int_arr_simple[nokta[1][2].x][nokta[1][2].y-1]; P13=int_arr_simple[nokta[1][3].x][nokta[1][3].y-1]; int P20,P21,P22,P23; P20=int_arr_simple[nokta[2][0].x][nokta[2][0].y-1]; P21=int_arr_simple[nokta[2][1].x][nokta[2][1].y-1]; P22=int_arr_simple[nokta[2][2].x][nokta[2][2].y-1]; P23=int_arr_simple[nokta[2][3].x][nokta[2][3].y-1]; int P30,P31,P32,P33; P30=int_arr_simple[nokta[3][0].x][nokta[3][0].y-1]; P31=int_arr_simple[nokta[3][1].x][nokta[3][1].y-1]; P32=int_arr_simple[nokta[3][2].x][nokta[3][2].y-1]; P33=int_arr_simple[nokta[3][3].x][nokta[3][3].y-1]; xline_1=line_find(P00,P01,P02,P03, x_cor-(int)x_cor); xline_2=line_find(P10,P11,P12,P13, x_cor-(int)x_cor); xline_3=line_find(P20,P21,P22,P23, x_cor-(int)x_cor); xline_4=line_find(P30,P31,P32,P33, x_cor-(int)x_cor); result=line_find(xline_1,xline_2,xline_3,xline_4,y_cor-(int)y_cor); return result; } int line_find(int P0,int P1,int P2,int P3, float x) { // bir denklemin "rengini" çevirmek için kullanılır.... float A,B,C,D,result; A=(float)(-(float)1/2)*(float)P0 + ((float)3/2)*(float)P1 + (-(float)3/2)*(float)P2 + ((float)1/2)*(float)P3 ; B=(float)P0 + (-(float)5/2)*(float)P1 + (2)*(float)P2 + (-(float)1/2)*(float)P3 ; C=(-(float)1/2)*(float)P0 + ((float)1/2)*(float)P2 ; D=(float)P1 ; result=A*x*x*x + B*x*x + C*x + D ; return result; } int main (){ readPpm("irfan.ppm"); save2Ppm("ppm",int_arr,255); save2Pgm("pgm",int_arr_simple,255); zooming_bilinear(); save2Pgm_zoom("zoom_bilinear",zoom_photo,255); zooming_bicubic(); save2Pgm_zoom("zoom_bicubic",zoom_photo_bicubic,255); return 0; }

降尺度的双立方插值

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