之前写过两篇博文，介绍了最近邻插值，双线性插值和9点插值算法的基本理论，今天用Matlab来验证，并简单对比一下效果。

之前的博文地址为：

http://blog.chinaaet.com/justlxy/p/5100052604

http://blog.chinaaet.com/justlxy/p/5100052609

考虑到ChinaAET会压缩上传的图片，所以博文中的图片仅供参考，具体可以参考本文最后的附件！

一、首先比较压缩效果

原图为1000*1000：压缩为500*500

1、最近邻插值：

2、双线性插值：

3、9点插值法（模式一）：

4、9点插值法（模式二）：

5、9点插值法（模式三）：

6、使用Win7自带画图工具：

二、下面比较放大效果：

原图为300*300：

1、最近邻插值法：

2、双向性插值法：

3、9点插值法（模式一）：

4、9点插值法（模式二）：

5、9点插值法（模式三）：

6、Win7系统画图工具效果：

附：Matlab源码：

function [ im_out ] = interpolation( im_in, dstWidth, dstHeight, mode ) %UNTITLED Summary of this function goes here % Detailed explanation goes here [srcWidth,srcHeight,temp] = size(im_in); if(mode == 1) %nearest_neighbor for dstX = 1:1:dstWidth for dstY = 1:1:dstHeight srcX = dstX * (srcWidth / dstWidth); srcY = dstY * (srcHeight / dstHeight); if(srcX < 1) srcX = 1; end if(srcX > srcWidth) srcX = srcWidth; end if(srcY < 1) srcY = 1; end if(srcY > srcWidth) srcY = srcWidth; end im_out(int16(dstX),int16(dstY),:) = im_in(int16(srcX),int16(srcY),:); end end end if(mode == 2) %bilinearity for dstX = 1:1:dstWidth for dstY = 1:1:dstHeight srcX = dstX * (srcWidth / dstWidth); srcY = dstY * (srcHeight / dstHeight); if(srcX < 1) srcX = 1; end if(srcX >= srcWidth) srcX = srcWidth - 1; end if(srcY < 1) srcY = 1; end if(srcY >= srcWidth) srcY = srcWidth - 1; end srcX_i = fix(srcX); srcX_f = srcX - srcX_i; srcY_i = fix(srcY); srcY_f = srcY - srcY_i; im_out(int16(dstX),int16(dstY),:) = (1 - srcX_f) * (1 - srcY_f) * im_in(int16(srcX_i),int16(srcY_i),:) + ... (1 - srcX_f) * srcY_f * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... srcX_f * (1 - srcY_f) * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... srcX_f * srcY_f * im_in(int16(srcX_i + 1),int16(srcY_i + 1),:); end end end if(mode == 3) % 9-point interpolation mode 1 for dstX = 1:1:dstWidth for dstY = 1:1:dstHeight srcX = dstX * (srcWidth / dstWidth); srcY = dstY * (srcHeight / dstHeight); if(srcX < 1) srcX = 1; end if(srcX >= srcWidth) srcX = srcWidth - 1; end if(srcY < 1) srcY = 1; end if(srcY >= srcWidth) srcY = srcWidth - 1; end srcX_i = fix(srcX); srcX_f = srcX - srcX_i; srcY_i = fix(srcY); srcY_f = srcY - srcY_i; if(srcX_f <= 0.5) if(srcY_f <= 0.5) %Area 1 im_out(int16(dstX),int16(dstY),:) = 0.5625 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.1875 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.1875 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.0625 * im_in(int16(srcX_i),int16(srcY_i),:); else %Area 3 im_out(int16(dstX),int16(dstY),:) = 0.1875 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.0625 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.5625 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.1875 * im_in(int16(srcX_i),int16(srcY_i),:); end else if(srcY_f <= 0.5) %Area 2 im_out(int16(dstX),int16(dstY),:) = 0.1875 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.5625 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.0625 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.1875 * im_in(int16(srcX_i),int16(srcY_i),:); else %Area 4 im_out(int16(dstX),int16(dstY),:) = 0.0625 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.1875 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.1875 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.5625 * im_in(int16(srcX_i),int16(srcY_i),:); end end end end end if(mode == 4) % 9-point interpolation mode 2 for dstX = 1:1:dstWidth for dstY = 1:1:dstHeight srcX = dstX * (srcWidth / dstWidth); srcY = dstY * (srcHeight / dstHeight); if(srcX < 1) srcX = 1; end if(srcX >= srcWidth) srcX = srcWidth - 1; end if(srcY < 1) srcY = 1; end if(srcY >= srcWidth) srcY = srcWidth - 1; end srcX_i = fix(srcX); srcX_f = srcX - srcX_i; srcY_i = fix(srcY); srcY_f = srcY - srcY_i; if(srcX_f <= 0.5) if(srcY_f <= 0.5) %Area 1 im_out(int16(dstX),int16(dstY),:) = 0.5 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.25 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.25 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0 * im_in(int16(srcX_i),int16(srcY_i),:); else %Area 3 im_out(int16(dstX),int16(dstY),:) = 0.25 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.5 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.25 * im_in(int16(srcX_i),int16(srcY_i),:); end else if(srcY_f <= 0.5) %Area 2 im_out(int16(dstX),int16(dstY),:) = 0.25 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.5 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.25 * im_in(int16(srcX_i),int16(srcY_i),:); else %Area 4 im_out(int16(dstX),int16(dstY),:) = 0 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.25 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.25 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.5 * im_in(int16(srcX_i),int16(srcY_i),:); end end end end end if(mode == 5) % 9-point interpolation mode 3 for dstX = 1:1:dstWidth for dstY = 1:1:dstHeight srcX = dstX * (srcWidth / dstWidth); srcY = dstY * (srcHeight / dstHeight); if(srcX < 1) srcX = 1; end if(srcX >= srcWidth) srcX = srcWidth - 1; end if(srcY < 1) srcY = 1; end if(srcY >= srcWidth) srcY = srcWidth - 1; end srcX_i = fix(srcX); srcX_f = srcX - srcX_i; srcY_i = fix(srcY); srcY_f = srcY - srcY_i; %Point Number Definition % 1 2 3 % 4 5 6 % 7 8 9 if(srcX_f <= 0.5) if(srcY_f <= 0.5) %Area 1 if(srcX_f <= 0.25) if(srcY_f <= 0.25) %Point No.1 point = 1; else %Ponit No.4 point = 4; end else if(srcY_f <= 0.25) %Point No.2 point = 2; else %Ponit No.5 point = 5; end end else %Area 3 if(srcX_f <= 0.25) if(srcY_f <= 0.75) %Point No.4 point = 4; else %Ponit No.7 point = 7; end else if(srcY_f <= 0.75) %Point No.5 point = 5; else %Ponit No.8 point = 8; end end end else if(srcY_f <= 0.5) %Area 2 if(srcX_f <= 0.75) if(srcY_f <= 0.25) %Point No.2 point = 2; else %Ponit No.5 point = 5; end else if(srcY_f <= 0.25) %Point No.3 point = 3; else %Ponit No.6 point = 6; end end else %Area 4 if(srcX_f <= 0.75) if(srcY_f <= 0.75) %Point No.5 point = 5; else %Ponit No.8 point = 8; end else if(srcY_f <= 0.75) %Point No.6 point = 6; else %Ponit No.9 point = 9; end end end end switch(point) case 1 im_out(int16(dstX),int16(dstY),:) = im_in(int16(srcX_i),int16(srcY_i),:); case 2 im_out(int16(dstX),int16(dstY),:) = 0.5 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.5 * im_in(int16(srcX_i + 1),int16(srcY_i),:); case 3 im_out(int16(dstX),int16(dstY),:) = im_in(int16(srcX_i + 1),int16(srcY_i),:); case 4 im_out(int16(dstX),int16(dstY),:) = 0.5 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.5 * im_in(int16(srcX_i),int16(srcY_i + 1),:); case 5 im_out(int16(dstX),int16(dstY),:) = 0.25 * im_in(int16(srcX_i),int16(srcY_i),:) + ... 0.25 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.25 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.25 * im_in(int16(srcX_i),int16(srcY_i),:); case 6 im_out(int16(dstX),int16(dstY),:) = 0.5 * im_in(int16(srcX_i + 1),int16(srcY_i),:) + ... 0.5 * im_in(int16(srcX_i + 1),int16(srcY_i + 1),:); case 7 im_out(int16(dstX),int16(dstY),:) = im_in(int16(srcX_i),int16(srcY_i + 1),:); case 8 im_out(int16(dstX),int16(dstY),:) = 0.5 * im_in(int16(srcX_i),int16(srcY_i + 1),:) + ... 0.5 * im_in(int16(srcX_i + 1),int16(srcY_i + 1),:); case 9 im_out(int16(dstX),int16(dstY),:) = im_in(int16(srcX_i + 1),int16(srcY_i + 1),:); otherwise im_out(int16(dstX),int16(dstY),:) = [0,0,0]; end end end end imshow(im_out); end

附件：

插值算法效果比较.docx