Matlab : Plot options with "set" fail when saving to eps and jpg - matlab

Question

I am using a script to get an automated data treatment (polynomial interpolation, tangent, ...), but when I use the function set to change my plot options before saving, I don't always get the right result : only the font option (see code) seem to work, while the image is really small and the background color doesn't change as it should.
What I would like is to have both eps and jpg files with the plot options I used. Writing this script, I kept adding/moving plot options, and I really don't understand why sometimes some options appear on the plot but seem to be ignored while saving.
Here is the part of my code that has all the plot options, I added those three first line instead of all my treatment.
t=linspace(0,10,10);
front=rand(1,10);
fit=front+rand(1,10)/2;
degre=1;
plot(t,fit,'-b','LineWidth',2);
hold on
grid on
plot(t,front,'.r','LineWidth',2);
hold off
l=legend({['Interpolation polynomiale de degre ',num2str(degre)],'Resultats experimentaux'});
set(l,'Color',[0.8 0.8 0.8])
set(gca,'FontSize',12,'FontWeight','bold','Color',[0.8 0.8 0.8]);
set(gcf, 'Units', 'pixels', 'Position', [0, 0, 1200, 1000])
xlabel('\fontsize{14}Temps de maintien (en s)')
ylabel('\fontsize{14}Distance parcourue (en mm)');
str='essai';
title(str)
filename='essai1';
saveas(gcf,filename,'jpg')
saveas(gcf,filename,'epsc2')
Trying to fix the resolution issue, I tried to change the default resolution using set(0, 'DefaultFigurePosition', [0 0 1200 1000]); but this line of code does not change anything
Thank you in advance

Answer 1

The background of the saved image will be white unless you set InvertHardcopy to off and for the size try 'PaperPositionMode'
set(gcf,'InvertHardcopy','off');
set(gcf,'PaperPositionMode','auto');
set(gcf,'Position', [0, 0, 2400, 2000]); %the resoultion you want

Answer 2

I managed to solve both issues on my example script, using
hFig = figure(1);
set(hFig, 'Position', [0 0 1200 1000])
before "plot", and
l=legend({['Interpolation polynomiale de degre ',num2str(degre)],'Resultats experimentaux'});
set(l,'Color',[0.8 0.8 0.8])
set(gca,'FontSize',12,'FontWeight','bold','Color',[0.8 0.8 0.8]);
set(gcf,'InvertHardcopy','off');
between plot and plot options.
However, this does not work with my main code, I am trying to put in comment most of my non-vital plot options and see what happens.
It would be great if someone could provide me with a better understanding of how those options work, I am mostly coding by try-and-error, but this is not the most efficient approach.
Edit I solved my problem, I had 4 plots on the same figure and I just wrote hold all instead of hold on
Looking at Matlab help, this shouldn't work, but it did.
hold all is the same as hold on.
Note: This syntax will be removed in a future release. Use hold on instead.
If anyone has an explanation as to why it worked, I would like to understand what happened.
Thank you