Matlab - Scaling Image Colorbar
How can I scale the axis of the colorbar
false color image?
I read this post and copied the code, but it doesn't seem to work correctly:
MATLAB Colorbar - Same Colors, Scaled Values
See two images below. In the first (no scaling) coloraxis goes
[1 2 3 4 5 6]*10^4
In the second image it goes
[0.005 0.01 0.015 0.02 0.025]
Correct scaling (with C = 100000
) would be
[0.1 0.2 0.3 0.4 0.5 0.6]
No scaling
Incorrect scaling
I want the coloraxis to be scaled 1/C
and I can freely choose C
so that when the pixel value = 10^4
and C=10^6
, the scale should show 10^-2
.
The reason I first multiply my image by C
is to get more decimal places because all values โโbelow 1 will display as zero without scaling C
.
When I run the code, I get yticks
as a workspace variable with the following values:
[500 1000 1500 2000 2500]
My code:
RGB = imread('IMG_0043.tif');% Read Image
info = imfinfo('IMG_0043.CR2'); % get Metadata
C = 1000000; % Constant to adjust image
x = info.DigitalCamera; % get EXIF
t = getfield(x, 'ExposureTime');% save ExposureTime
f = getfield(x, 'FNumber'); % save FNumber
S = getfield(x, 'ISOSpeedRatings');% save ISOSpeedRatings
date = getfield(x,'DateTimeOriginal');
I = rgb2gray(RGB); % convert Image to greyscale
K = 480; % Kamerakonstante(muss experimentel eavaluiert werden)
% N_s = K*(t*S)/power(f,2))*L
L = power(f,2)/(K*t*S)*C; %
J = immultiply(I,L); % multiply each value with constant , so the Image is Calibrated to cd/m^2
hFig = figure('Name','False Color Luminance Map', 'ToolBar','none','MenuBar','none');
% Create/initialize default colormap of jet.
cmap = jet(16); % or 256, 64, 32 or whatever.
% Now make lowest values show up as black.
cmap(1,:) = 0;
% Now make highest values show up as white.
cmap(end,:) = 1;
imshow(J,'Colormap',cmap) % show Image in false color
colorbar % add colorbar
h = colorbar; % define colorbar as variable
y_Scl = (1/C);
yticks = get(gca,'YTick');
set(h,'YTickLabel',sprintfc('%g', [yticks.*y_Scl]))
ylabel(h, 'cd/m^2')% add unit label
title(date); % Show date in image
caxis auto % set axis to auto
datacursormode on % enable datacursor
img = getframe(gcf);
nowstr = datestr(now, 'yyyy-mm-dd_HH_MM_SS');
folder = 'C:\Users\Taiko\Desktop\FalseColor\';
ImageFiles = dir( fullfile(folder, '*.jpg') );
if isempty(ImageFiles)
next_idx = 1;
else
lastfile = ImageFiles(end).name;
[~, basename, ~] = fileparts(lastfile);
file_number_str = regexp('(?<=.*_)\d+$', basename, 'match' );
last_idx = str2double(file_number_str);
next_idx = last_idx + 1;
end
newfilename = fullfile( folder, sprintf('%s_%04d.jpg', nowstr, next_idx) );
imwrite(img.cdata, newfilename);
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Problems:
1) You get YTick
shapes ( gca
) but not a color bar. This will give you the "pixel" coordinates of the plot, not the actual values. Use yticks = get(h,'YTick');
.
2) caxis auto
Should appear before overwriting YTicks
(and after turning on the color panel); otherwise, the scale and ticks will be inconsistent.
3) Do you mean C = 100000
?
Result:
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