How to save image as pixel by pixel size and without white background

Hello, I would like to seek help for the image save as bmp.file with pixel by pixel size and without white background.

clear all; close all; clc

X = [-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150];
Y = [-150,-150,-150,-150,-150,-150,-150,-150,-150,-150,-150,-150,-150;-125,-125,-125,-125,-125,-125,-125,-125,-125,-125,-125,-125,-125;-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100;-75,-75,-75,-75,-75,-75,-75,-75,-75,-75,-75,-75,-75;-50,-50,-50,-50,-50,-50,-50,-50,-50,-50,-50,-50,-50;-25,-25,-25,-25,-25,-25,-25,-25,-25,-25,-25,-25,-25;0,0,0,0,0,0,0,0,0,0,0,0,0;25,25,25,25,25,25,25,25,25,25,25,25,25;50,50,50,50,50,50,50,50,50,50,50,50,50;75,75,75,75,75,75,75,75,75,75,75,75,75;100,100,100,100,100,100,100,100,100,100,100,100,100;125,125,125,125,125,125,125,125,125,125,125,125,125;150,150,150,150,150,150,150,150,150,150,150,150,150];
r_M = [27,19,12,8,3,3,1,0,0,3,9,15,23;30,20,14,9,5,3,1,0,0,3,7,12,21;33,23,15,11,6,3,2,1,2,4,7,13,20;33,23,15,12,7,4,2,2,2,4,7,12,19;30,20,16,13,8,5,3,3,4,5,7,12,20;27,20,16,14,9,6,4,4,5,5,7,12,21;27,20,16,14,8,5,3,3,4,4,6,11,20;27,19,15,13,7,5,3,2,3,4,6,12,21;25,18,14,12,6,4,2,2,3,4,6,11,21;28,19,15,13,7,4,2,2,3,4,7,13,23;29,19,15,13,8,5,3,2,2,4,7,15,25;33,22,17,14,8,5,3,2,2,3,5,12,23;37,25,19,15,8,6,4,2,1,2,2,10,19];

figure(3)
contourf(X,Y,r_M,2560,'LineColor','none')
shading interp
axis square
% colorbar
% caxis([0 4])
colormap(flipud(gray(256)));
set(gca,'xtick',[])
set(gca,'ytick',[])

% %-------save compensation hologram-------
name = 'hologram';
fpath = 'C:\Users\Admin\Desktop';
saveas(gca, fullfile(fpath, name), 'bmp');

Answer 1

[DGM]

Getting figures saved in a particular way is always a challenge, and the methods vary with versions. Personally, I just use export_fig()

https://www.mathworks.com/matlabcentral/fileexchange/23629-export_fig

set(gca,'units','pixels')
origpos=get(gca,'position');
origpos(3)=399; % 400-1
set(gca,'position',origpos)

outpict=export_fig('-a2','-m1');

This gives me a 400x400 close-cropped image, and should work so long as the figure window is big enough. You can just save the image as needed.

imwrite(outpict,'finallyworks.png')

[Tina Hsiao]

I got the error as below,

export_fig error. Please ensure:

* that the function you used (E:\file\export_fig.m) version 3.14 is from the expected location

Unrecognized function or variable 'hyperlink'.

Error in export_fig (line 1199)

fprintf(2, ' * and that you did not made a mistake in

export_fig''s %s\n', hyperlink('matlab:help

export_fig','expected input arguments'));

Error in untitled (line 19)

outpict=export_fig('-a2','-m1');

My code as below (Matlab 2017a version), could you please help me fix it? Thanks a lot

clear all; close all; clc
X = [-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150;-150,-125,-100,-75,-50,-25,0,25,50,75,100,125,150];
Y = [-150,-150,-150,-150,-150,-150,-150,-150,-150,-150,-150,-150,-150;-125,-125,-125,-125,-125,-125,-125,-125,-125,-125,-125,-125,-125;-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100,-100;-75,-75,-75,-75,-75,-75,-75,-75,-75,-75,-75,-75,-75;-50,-50,-50,-50,-50,-50,-50,-50,-50,-50,-50,-50,-50;-25,-25,-25,-25,-25,-25,-25,-25,-25,-25,-25,-25,-25;0,0,0,0,0,0,0,0,0,0,0,0,0;25,25,25,25,25,25,25,25,25,25,25,25,25;50,50,50,50,50,50,50,50,50,50,50,50,50;75,75,75,75,75,75,75,75,75,75,75,75,75;100,100,100,100,100,100,100,100,100,100,100,100,100;125,125,125,125,125,125,125,125,125,125,125,125,125;150,150,150,150,150,150,150,150,150,150,150,150,150];
r_M = [27,19,12,8,3,3,1,0,0,3,9,15,23;30,20,14,9,5,3,1,0,0,3,7,12,21;33,23,15,11,6,3,2,1,2,4,7,13,20;33,23,15,12,7,4,2,2,2,4,7,12,19;30,20,16,13,8,5,3,3,4,5,7,12,20;27,20,16,14,9,6,4,4,5,5,7,12,21;27,20,16,14,8,5,3,3,4,4,6,11,20;27,19,15,13,7,5,3,2,3,4,6,12,21;25,18,14,12,6,4,2,2,3,4,6,11,21;28,19,15,13,7,4,2,2,3,4,7,13,23;29,19,15,13,8,5,3,2,2,4,7,15,25;33,22,17,14,8,5,3,2,2,3,5,12,23;37,25,19,15,8,6,4,2,1,2,2,10,19];
figure(3)
contourf(X,Y,r_M,2560,'LineColor','none')
shading interp
axis square
% colorbar
% caxis([0 4])
colormap(flipud(gray(256)));
set(gca,'xtick',[])
set(gca,'ytick',[])

set(gca,'units','pixels')
origpos=get(gca,'position');
origpos(3)=399; % 400-1
set(gca,'position',origpos)
outpict=export_fig('-a2','-m1');
imwrite(outpict,'finallyworks.png')

[Tina Hsiao]

I solve it. Thanks a lot.

[DGM]

How did you unpack the zip file? I imagine one of two things happened. Either you didn't unpack all the files, or when you added them to the path, you didn't add all of them. It's usually more convenient to have them all together in a dedicated directory and then add that whole directory to the path.

You can check by:

which export_fig
which hyperlink
which isolate_axes

etc

[DGM]

Ah well good!