Frame around an image

Hi.

I'm trying to wrap a frame around an image in matlab, but I can't get it working. I get the following error message:

Error using ==> image TrueColor CData contains element out of range 0.0 <= value <= 1.0

But the color array should already be of type uint8, converted by using the cast-command.

Any help will be appreciated! Thank you.

Btw, i'm a Matlab rookie :)

My code:

[X, cmapX] = readimage('images/RGB_Colored/Lena.tif');
dimX = size(X); 
if numel(dimX)==2, dimX = [dimX 1]; end;

width = 100; % of the frame

color = [229 67 0];
color = reshape(color,1,1,numel(color));

color = cast(color,class(X)); % same type as X, uint8

h=dimX(1); w=dimX(2); d=dimX(3);

newW = w+2*width;
newH = h+2*width;

img = zeros(newH,newW,d); % zerofilled array

img(1,1,1:end)=color(:,:,1:end);

img(width+1:1:newH-width,width+1:1:newW-width,:)=X;

Y = img;

cmapY = cmapX;

if dimX(3)==1
  xwindow = figure('Name','Nuværende billede');
  image(ind2rgb(Y,cmapX));
  axis image off
elseif dimX(3)==3
  xwindow = figure('Name','Nuværende billede');
  image(Y);
  axis image off
else
  disp('error');
end

Answer 1

[Walter Roberson]

This statement;

img = zeros(newH,newW,d);

That creates a double array, not an array of the same data type as "color".

Answer 2

[Nicolai]

Thank you for your reply.

I see. What function should I use to make an array containing the frame and the picture then? If I translate zeros with cast to uint8, I get 0.

I tried

img = repmat(color,[newH newW d]);

But I get error with that too. What I am looking for is a array I can fill with a color like this

color = [229 67 0];

And then afterward insert the image. Inserting the image is working fine.

[Walter Roberson]

img = zeros(newH,newW,d,'uint8');

If you want to make img repeated copies of color, then

img = repmat(color,newH,newW,1);

Please re-check your image insertion code, and consider the cases:

1) you read in a truecolor (3D) image. The colormap will always be empty for this

2) you read in a grayscale (2D) image. The colormap will be empty for this.

3) you read in a pseudocolor (2D) image. The colormap will not be empty for this.

Consider that you are always creating a 3D matrix, img, but sometimes you are only copying X in to the first pane if it (:,:,1). Where your original was 2D or not, img is 3D. Then Y = img. Then if the original image was 2D, you try to use ind2rgb(Y,cmapX) which is not legal because Y is going to be 3D.

Answer 3

[Image Analyst]

Try this:

padRows = 100;
padCols = 50;
newImageR = padarray(rgbImage(:,:,1), [padRows padCols], 229);
newImageG = padarray(rgbImage(:,:,2), [padRows padCols], 67);
newImageB = padarray(rgbImage(:,:,3), [padRows padCols], 0);
newRGB = cat(3, newImageR, newImageG, newImageB);

padArray works on color images but not if you want different colored padding in each color channel. That's why I did it three times.