How to place pregenerated image (double) on top of an opened image with transparency?

Dear All,

I have a question how to add a scale bar (rooler) on top of the image (the example of result image is below).

In my code i have created the below image by:

1) drawing a black and white rooler and saving it as png file

2) I open both the required image and the rooler image and place one on top of another with appropriate "AlphaData" to get transparency.

Here is the question. How I can omit saving/opening the rooler??? The entire code is beelow the image.

Many thanks for the hepl and ideas

% the script draw a roller(scale bar) in micromiters (um) on imported image

% Options:

% 1) the scale of the rooler is CHANGING depending on the magnification.

% 2) The scale size remains as requested, but the size of the rooler changes

% input arguments:

% image fileName,

% coordinates of a defect,

% magnification

clear all;close all

folderName2save='..\export_with_rooles';

Input arguments

% ID of the frame

frameID="226456454";

% the image on which the rooles has to be placed

fileName='C:\Users\sns\Documents\P-Frames\Defektenanerkenung\MatlabScripts\rooler\image0007.jpg';

%position where the rooler has to beplaces on the image

position=[600,300];% has to be an input argument)

% maginificaitons value used in a microscope to inspect the frames. Relation coeficients um/px are stored in the file Re-scale.excel

magn=5;

% select an option with fixed rooles: "yes" or not "no"

RoolerScale="yes";

% fixed scales of the roole

widthFixed=[100, 200, 300]

TfontSize=14;

Exporting data

filePathR='..\export_with_rooles\temp\'; % file path for the rooler

FileNameR=sprintf("rooler_ID%s_X%d_%s.png",frameID,magn,string(datestr(now,'mm-dd-yyyy HH-MM')));

filePath='..\export_with_rooles\'; % file path for the images with rooler

FileName=sprintf("ID%s_X%d_%s_defects.png",frameID,magn,string(datestr(now,'mm-dd-yyyy HH-MM')))

Reading the magnification factor

my_excel=readtable('C:\Users\sns\Documents\P-Frames\Defektenanerkenung\MatlabScripts\rooler\Re-scale.xlsx',VariableNamingRule='modify');

idx=(my_excel.Magnification==magn); % finding the correct correction factor according to magnification

correctFactor=my_excel.AverageValueOfPixelSize_um_px_(idx) % um/px

clear my_excel idx

Drawing the rooler with changeble scale

%parameters of the rooler

heightR=[15]; % height of the rooler

widthR=[25,50,100,150]; % width in pixels and number of elements of the rooler

TextcorrectFactor=correctFactor;

% if the scale of the rooler has to be fixed:

if RoolerScale=="yes"

widthR=round(widthFixed./correctFactor,0);

TfontSize=12;

end

TextcorrectFactor=correctFactor*0.2;

borders=[5]; % border on top/bottom of the rooler

% generation of the horisontal rooler

rooler=[];

for i=1:length(widthR)

rooleri=[zeros(heightR,widthR(1,i));ones(heightR,widthR(1,i))];

rooleri(end-borders:end,:)=0;

if rem(i,2)==0

rooler=[rooler,flip(rooleri)];

else

rooler=[rooler,rooleri];

end

end

clear i idx my_excel

rooler=[ones(size(rooler));rooler];

roolerHeight=size(rooler,1);

HVrooler=ones(sum(size(rooler))); % rooler canvas

HVrooler(1:roolerHeight,roolerHeight+1:end)=rooler ;

HVrooler(roolerHeight+1:end,1:roolerHeight)=rooler';

% text on the rooler with correction according to the magnification

my_text=string(fix(round(widthR.*correctFactor,0)));

if RoolerScale=="yes"

my_text=string(widthFixed)

end

%rooler saving as a png file and transparency

A=double(HVrooler==0);

f=fullfile(filePathR,FileNameR);

imwrite(HVrooler,f, 'Alpha',A);

f2=fullfile(filePathR,'Alphachanel');

save(f2,'A');

placing the rooler on an image

% reading the image for analysis

Image =imread(fileName);

imshow(Image);

hold on

% loading the pregenerated rooles and the alpha chennel

roolerImage=imread(f);

load(f2,"A")

% combining the rooler and the images

image(position(1,1),position(1,2),roolerImage,"AlphaData",A);

% placeing the velues for the rooler

for i=1:length(my_text)

X=roolerHeight+widthR(1,i)*(i-1)/2+position(1,1);

Y=0+position(1,2);

if i==length(my_text)

my_text(1,i)=append(num2str(my_text(1,i))," (um)");

text(X, Y,my_text(1,i),'Color','b','FontSize',TfontSize)

else

text(X, Y,my_text(1,i),'Color','b','FontSize',TfontSize)

end

end

saving the resulted image with the rooler on top

f=fullfile(folderName2save,FileName);

saveas(gcf,f)

Answer 1

[DGM]

If you're generating a ruler image each time and don't need to save a copy, then just don't save a copy.

folderName2save='';

% ID of the frame
frameID="226456454";
% the image on which the rooles has to be placed
%fileName='C:\Users\sns\Documents\P-Frames\Defektenanerkenung\MatlabScripts\rooler\image0007.jpg';
fileName = 'peppers.png';

%position where the rooler has to beplaces on the image
position=[50,10];% has to be an input argument (adjusted for test image)
% maginificaitons value used in a microscope to inspect the frames. Relation coeficients um/px are stored in the file Re-scale.excel
magn=5;
% select an option with fixed rooles: "yes" or not "no"
RoolerScale="yes";

% fixed scales of the roole
widthFixed=[100, 200, 300]

widthFixed = 1×3

100 200 300

TfontSize=14;

%Exporting data
filePathR='./'; % file path for the rooler
FileNameR=sprintf("rooler_ID%s_X%d_%s.png",frameID,magn,string(datestr(now,'mm-dd-yyyy HH-MM')));
filePath='./'; % file path for the images with rooler
FileName=sprintf("ID%s_X%d_%s_defects.png",frameID,magn,string(datestr(now,'mm-dd-yyyy HH-MM')))

FileName = "ID226456454_X5_10-19-2022 19-22_defects.png"

%Reading the magnification factor
%my_excel=readtable('C:\Users\sns\Documents\P-Frames\Defektenanerkenung\MatlabScripts\rooler\Re-scale.xlsx',VariableNamingRule='modify');
%idx=(my_excel.Magnification==magn); % finding the correct correction factor according to magnification
%correctFactor=my_excel.AverageValueOfPixelSize_um_px_(idx) % um/px
%clear my_excel idx
correctFactor = 2; % idk what's in that file, so i'm just going to guess

%Drawing the  rooler with changeble scale
%parameters of the rooler
heightR=[15];           % height of the rooler
widthR=[25,50,100,150]; % width in pixels and number of elements of the rooler
TextcorrectFactor=correctFactor;

% if the scale of the rooler has to be fixed:
if RoolerScale=="yes"
    widthR=round(widthFixed./correctFactor,0);
    TfontSize=12;
end
TextcorrectFactor=correctFactor*0.2;
borders=[5];             % border on top/bottom of the rooler

% generation of the horisontal rooler
rooler=[];
for i=1:length(widthR)
    rooleri=[zeros(heightR,widthR(1,i));ones(heightR,widthR(1,i))];
    rooleri(end-borders:end,:)=0;
    if rem(i,2)==0
        rooler=[rooler,flip(rooleri)];
    else
        rooler=[rooler,rooleri];
    end
end
clear i idx my_excel

rooler=[ones(size(rooler)); rooler];
roolerHeight=size(rooler,1);
HVrooler=ones(sum(size(rooler))); %  rooler canvas
HVrooler(1:roolerHeight,roolerHeight+1:end)=rooler ;
HVrooler(roolerHeight+1:end,1:roolerHeight)=rooler';

% text on the rooler with correction according to the magnification
my_text=string(fix(round(widthR.*correctFactor,0)));
if RoolerScale=="yes"
    my_text=string(widthFixed)
end

my_text = 1×3 string array
    "100"    "200"    "300"

% create transparency
A = double(HVrooler==0); % this is the alpha


%placing the rooler on an image
% reading the image for analysis
Image = imread(fileName);
imshow(Image);
hold on

% combining the rooler and the images
% just use the generated images
image(position(1,1),position(1,2),HVrooler,"AlphaData",A);

% placeing the velues for the rooler
for i=1:length(my_text)
    X=roolerHeight+widthR(1,i)*(i-1)/2+position(1,1);
    Y=0+position(1,2);
    if i==length(my_text)
        my_text(1,i)=append(num2str(my_text(1,i))," (um)");
        text(X, Y,my_text(1,i),'Color','b','FontSize',TfontSize)
    else
        text(X, Y,my_text(1,i),'Color','b','FontSize',TfontSize)
    end
end

%saving the resulted image with the rooler on top
f=fullfile(folderName2save,FileName);
saveas(gcf,f)

Bear in mind that the color of the ruler overlay now depends on the current colormap. The same goes for any single-channel image.

If you wanted to save the images with transparency, you don't need to save alpha as a .mat file. PNG supports alpha content; you'd just have to read it when you call imread().