如何使用 MATLAB 自动填充任意图像？

2024-01-02

这是基于此答案的进一步问题：

如何在 MATLAB 中实现鱼眼镜头效果（桶形变换）？ https://stackoverflow.com/questions/2589851/how-can-i-implement-this-visual-effect-in-matlab/2589957#2589957

一般解决方案应该适用于所有背景颜色和长/宽比。

通常情况下，在 MATLAB 中可以通过多种不同的方法来执行此操作。我将列出一些填充示例RGB 图像 http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-20224...

解决方案#1：添加填充CAT http://www.mathworks.com/access/helpdesk/help/techdoc/ref/cat.html制作方形图像

该解决方案采用给定的颜色padColor并使用该函数复制它REPMAT http://www.mathworks.com/access/helpdesk/help/techdoc/ref/repmat.html创建正确尺寸、形状和颜色的填充。然后使用该函数将填充添加到图像的两侧CAT http://www.mathworks.com/access/helpdesk/help/techdoc/ref/cat.html:

[r,c,d] = size(rgbImage);  %# Get the image dimensions
nPad = abs(c-r)/2;         %# The padding size
padColor = [1 1 1];        %# RGB triple for pad color (white)
padColor = reshape(padColor,1,1,3);  %# Reshape pad color to 1-by-1-by-3
if c > r                   %# Pad rows
  newImage = cat(1,repmat(padColor,floor(nPad),c),...  %# Top padding
                   rgbImage,...                        %# Image
                   repmat(padColor,ceil(nPad),c));     %# Bottom padding
elseif r > c               %# Pad columns
  newImage = cat(2,repmat(padColor,r,floor(nPad)),...  %# Left padding
                   rgbImage,...                        %# Image
                   repmat(padColor,r,ceil(nPad)));     %# Right padding
end

您可以修改上述解决方案以适用于indexed http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-17587, 灰度 http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-13941, or 二值图像 http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-33397通过替换定义的两行padColor与以下之一：

padColor = uint8(1);    %# For an indexed image (index of color to use)
padColor = uint8(255);  %# For a grayscale image (white)
padColor = true;        %# For a binary image (white)

解决方案#2：制作空白方形图像并插入原始图像

该解决方案采用给定的颜色padColor并使用该函数复制它REPMAT http://www.mathworks.com/access/helpdesk/help/techdoc/ref/repmat.html创建该颜色的空白方形图像。然后将原始图像插入到该空白图像的居中位置：

[r,c,d] = size(rgbImage);  %# Get the image dimensions
padColor = [1 1 1];        %# RGB triple for pad color (white)
padColor = reshape(padColor,1,1,3);  %# Reshape pad color to 1-by-1-by-3
if c > r                   %# Pad rows
  newImage = repmat(padColor,c);  %# Make c-by-c-by-3 matrix of given color
  rowIndex = floor((c-r)/2);      %# Row index for inserting image
  newImage(rowIndex+(1:r),:,:) = rgbImage;     %# Insert the image
elseif r > c               %# Pad columns
  newImage = repmat(padColor,r);  %# Make r-by-r-by-3 matrix of given color
  columnIndex = floor((r-c)/2);   %# Column index for inserting image
  newImage(:,columnIndex+(1:c),:) = rgbImage;  %# Insert the image
end

padColor = uint8(1);    %# For an indexed image (index of color to use)
padColor = uint8(255);  %# For a grayscale image (white)
padColor = true;        %# For a binary image (white)

解决方案#3：使用PADARRAY http://www.mathworks.com/access/helpdesk/help/toolbox/images/padarray.html

该解决方案使用该功能PADARRAY http://www.mathworks.com/access/helpdesk/help/toolbox/images/padarray.html创建填充以使图像成为正方形。不幸的是，没有简单的方法来指定您想要的填充颜色RGB 图像 http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-20224使用此解决方案时（见下文）。但是，您可以使用'replicate'论点有PADARRAY http://www.mathworks.com/access/helpdesk/help/toolbox/images/padarray.html只需在添加填充的图像边缘复制颜色：

[r,c,d] = size(rgbImage);  %# Get the image dimensions
nPad = abs(c-r)/2;         %# The padding size
if c > r                   %# Pad rows
  newImage = padarray(rgbImage,[floor(nPad) 0],...  %# Pad top
                      'replicate','pre');
  newImage = padarray(newImage,[ceil(nPad) 0],...   %# Pad bottom
                      'replicate','post');
elseif r > c               %# Pad columns
  newImage = padarray(rgbImage,[0 floor(nPad)],...  %# Pad left
                      'replicate','pre');
  newImage = padarray(newImage,[0 ceil(nPad)],...   %# Pad right
                      'replicate','post');
end

该解决方案适用于indexed http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-17587, 灰度 http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-13941, or 二值图像 http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-33397。对于这三种图像类型，您可以选择替换'replicate'带有要用于填充的标量值的参数（即uint8(255)用于灰度图像中的白色填充）。为了RGB 图像 http://www.mathworks.com/access/helpdesk/help/toolbox/images/f14-13543.html#f14-20224，替换'replicate'具有单个值的参数将只允许您创建从白色到黑色的灰色阴影（即，1创建白色填充）。

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