MATLAB Answers

Combine Images to display on single page

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Cg Gc
Cg Gc on 2 Jan 2019
Commented: Image Analyst on 9 Jan 2019
I have multiple sets of 21 images that I would like to display either as a single image or as on one page, which ever is easier. For simplicity I only uploaded 4 here.
I have tried the code below, but I received error messages.
fileFolder = fullfile(matlabroot,'toolbox','images','imdata');
dirOutput = dir(fullfile(fileFolder,'trajplot_*.png'));
fileNames = string({dirOutput.name});
montage(fileNames, 'Size', [2 2]);
Error using montage>getImagesFromFiles (line 366)
FILENAMES must be a cell array of strings or character vectors.
Error in montage>parse_inputs (line 243)
[I,cmap] = getImagesFromFiles(varargin{1});
Error in montage (line 114)
[I,cmap,mSize,indices,displayRange,parent] = parse_inputs(varargin{:});
img1 = imread('trajplot_C1_0012_10m.png');
img2 = imread('trajplot_C2_0012_10m.png');
img3 = imread('trajplot_C3_0012_10m.png');
img4 = imread('trajplot_C5_0012_10m.png');
>> multi = cat(3,img1,img2,img3);
>> montage(multi);
Error using images.internal.imageDisplayValidateParams>validateCData (line
115)
Multi-plane image inputs must be RGB images of size MxNx3.
Error in images.internal.imageDisplayValidateParams (line 27)
common_args.CData = validateCData(common_args.CData,image_type);
Error in images.internal.imageDisplayParseInputs (line 78)
common_args = images.internal.imageDisplayValidateParams(common_args);
Error in imshow (line 241)
images.internal.imageDisplayParseInputs({'Parent','Border','Reduce'},preparsed_varargin{:});
Error in montage (line 156)
hh = imshow(bigImage, displayRange,parentArgs{:});
>> multi = cat(4,img1,img2,img3,img4);
>> montage(multi);
%%The image shows up, but is one giant black square.%%
img1 = imread('trajplot_C1_0012_10m.jpeg');
img2 = imread('trajplot_C2_0012_10m.jpeg');
img3 = imread('trajplot_C3_0012_10m.jpeg');
>> multi = cat(3,img1,img2,img3);
montage(multi);
Error using images.internal.imageDisplayValidateParams>validateCData
(line 115)
Multi-plane image inputs must be RGB images of size MxNx3.
Error in images.internal.imageDisplayValidateParams (line 27)
common_args.CData = validateCData(common_args.CData,image_type);
Error in images.internal.imageDisplayParseInputs (line 78)
common_args = images.internal.imageDisplayValidateParams(common_args);
Error in imshow (line 241)
images.internal.imageDisplayParseInputs({'Parent','Border','Reduce'},preparsed_varargin{:});
Error in montage (line 156)
hh = imshow(bigImage, displayRange,parentArgs{:});
Does anyone know what is going on? Are my images in the wrong format or possibly too big?
The original files are in .ps format and were converted to .png using an online converter. If they need to be converted into something else, please let me know.

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Answers (2)

Image Analyst
Image Analyst on 2 Jan 2019
They appear, from the error message, to not be RGB images. Do they have an alpha plane or something?
What does this say?
whos img1
size(img1)
If it's not 3 planes, then you might take the first 3, if those represent R, G, and B.
img1 = img1(:,:,1:3);
or somehow otherwise process it until you get 3 planes. Attach two of your PNG files if you need more help.

  1 Comment

Cg Gc
Cg Gc on 2 Jan 2019
Name Size Bytes Class Attributes
img1 2275x1758x3 11998350 uint8
ans =
2275 1758 3

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Image Analyst
Image Analyst on 2 Jan 2019
Don't cat() them together into a 4-D array, just use montage():
multi = montage(img1,img2,img3,img4);

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Show 6 older comments
Cg Gc
Cg Gc on 7 Jan 2019
Those are the images. I will try a newer version. I am running 2017b. Thank you for your help.
Cg Gc
Cg Gc on 8 Jan 2019
I finally upgraded to 2018b and the code works. Thank you!
Last questions. Can the images be in color? Do you know how to get rid of the huge border and make the images larger and less blurry? The border is at least 2 inches wide and makes printing the images a nightmare.
Image Analyst
Image Analyst on 9 Jan 2019
I think the alpha channel can only be gray scale, not RGB, so you're better off trying to get them saved in a normal way in the first place, rather than how they are now.
To get rid of the border, try thresholding and cropping after the montage has been made.

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