Rotate one image and plot on top of another

Hello,

I am trying to plot two images on top of one another. The code included allows me to rotate the human torso by a defined angle, and then plot it on top of the other image (lower legs and protractor). My problem is that when I do so, the bottom image becomes much lighter than the top image, and when the top image crosses over the bottom image, the parts of the bottom image can still be seen. How do I solve these two problems?

% reading in the two images
Protractor = importdata('STS_Protractor2.jpg');
Torso = importdata('STS_Torso2.jpg'); % top of midline is at (349,304) (349.5,316)

RotationPoint = [510,745]; % This is the point the Torso image will be rotated around (center of hip)
Protractor_0 = [510,135]; % location of the 0 value on the protractor
LineLength = 500; % Length of the line centered on the torso and extending past the head

Angle = 25;
timeperiod = 'Pre00';

% rotate trunk image by max trunk angle from model output data, then format image so it can be placed on top of protractor image
TrunkAngle_Rotation = rotateAround(Torso,RotationPoint(2),RotationPoint(1),-Angle, 'crop'); % (image,y-coord,x-cord,angle,'variable') - Allows for rotation of torso image
Clear_Background = ~rotateAround(true(size(Torso)),RotationPoint(2),RotationPoint(1),-Angle); % When image is rotated, this changes the background to white rather than leaving black space. 
TrunkAngle_Rotation(Clear_Background&~imclearborder(Clear_Background)) = 255; % Redefines the variable to include the new white background 

% Plotting the two figures ontop of each other 
figure;
image([0 1084], [0 1084],Protractor);% First plotting the protractor background (maintaining the 1084 x 1084 image size) 
hold on
image([0 1084], [0 1084],TrunkAngle_Rotation) % Plotting trunk angle image 
alpha(.90)
hold on 
axis off

% Set the size for the figure
set(gcf, 'Units', 'Normalized', 'OuterPosition', [.5, .5, 0.19, 0.311]);

Thanks in advance.

Answer 1

[DGM]

Since the images are the same size, this can be done with a simple blend, without the need for any compositing.

% reading in the two images
Protractor = importdata('STS_Protractor2.jpg');
Torso = importdata('STS_Torso2.jpg'); % top of midline is at (349,304) (349.5,316)

RotationPoint = [510,745]; % This is the point the Torso image will be rotated around (center of hip)
Protractor_0 = [510,135]; % location of the 0 value on the protractor
LineLength = 500; % Length of the line centered on the torso and extending past the head

Angle = 25;
timeperiod = 'Pre00';

% rotate trunk image by max trunk angle from model output data, then format image so it can be placed on top of protractor image
TrunkAngle_Rotation = rotateAround(Torso,RotationPoint(2),RotationPoint(1),-Angle, 'crop'); % (image,y-coord,x-cord,angle,'variable') - Allows for rotation of torso image
Clear_Background = ~rotateAround(true(size(Torso)),RotationPoint(2),RotationPoint(1),-Angle); % When image is rotated, this changes the background to white rather than leaving black space. 
TrunkAngle_Rotation(Clear_Background) = 255; % Redefines the variable to include the new white background 

% blend the two images using a "darken" blend
outpict = min(Protractor,TrunkAngle_Rotation);

% Plotting the output image
imshow(outpict,'border','tight');

Note that there's nothing preventing the hand and torso from obscuring the thigh. That can be addressed.

% reading in the two images
Protractor = importdata('STS_Protractor2.jpg');
Torso = importdata('STS_Torso2.jpg'); % top of midline is at (349,304) (349.5,316)

RotationPoint = [510,745]; % This is the point the Torso image will be rotated around (center of hip)
Protractor_0 = [510,135]; % location of the 0 value on the protractor
LineLength = 500; % Length of the line centered on the torso and extending past the head

Angle = 25;
timeperiod = 'Pre00';

% create a mask
mask = imfill(im2gray(Torso)<250,'holes');
mask = bwareafilt(mask,1);
imshow(mask,'border','tight');

% rotate trunk image by max trunk angle from model output data, then format image so it can be placed on top of protractor image
TrunkAngle_Rotation = rotateAround(Torso,RotationPoint(2),RotationPoint(1),-Angle, 'crop'); % (image,y-coord,x-cord,angle,'variable') - Allows for rotation of torso image
Clear_Background = ~rotateAround(true(size(Torso)),RotationPoint(2),RotationPoint(1),-Angle); % When image is rotated, this changes the background to white rather than leaving black space. 
TrunkAngle_Rotation(Clear_Background) = 255; % Redefines the variable to include the new white background 
mask = rotateAround(mask,RotationPoint(2),RotationPoint(1),-Angle, 'crop'); % rotate the mask

% blank the background where the FG overlaps
Protractor(repmat(mask,[1,1,size(Protractor,3)])) = 255;

% blend the two images using a "darken" blend
outpict = min(Protractor,TrunkAngle_Rotation);

% Plotting the two figures ontop of each other 
imshow(outpict,'border','tight');

... although I suppose that's still kind of wrong. I guess the arm and torso could be masked separately, but I don't know how far you want to go with that. The concept of carrying the mask through the transformation should hold.

Using an RGBA workflow would simplify this a bit, but not with standard IPT/MATLAB tools.

[Josh Tome]

Yes!!! While there's still something artistically off about where the torso meets the thigh (looks like the right leg is missing and the left leg is behind the torso) this looks great. Thanks for the help!

[Image Analyst]

@DGM Just wondering, how did you get his rotateAround.m? Doesn't look like he ever attached it.

[DGM]

https://www.mathworks.com/matlabcentral/fileexchange/40469-rotate-an-image-around-a-point

Answer 2

[Image Analyst]

Try creating a new image by replacing only the parts of the rotated one where it's not white. Like

mask = TrunkAngle_Rotation < 200; % A 3-D RGB image since TrunkAngle_Rotation is color.
combinedImage = Protractor; % Initialize
combinedImage(mask) = 0; % Blacken where the mask is.
imshow(combinedImage);

If the blue line is not blue and you want it blue, then you may have to adapt it a bit.

[Josh Tome]

Yes, this works. The blue line also is still blue with your code.

Any thoughts on how to eliminate the parts of the bottom image (thigh and chair) that show through on the top image (torso). For instance, I can see parts of the thigh and chair through the arm/hand.

[Image Analyst]

Do you simply want to paste a cropped version of the image on top of the other one. You can crop it and paste it using something like the attached demos. Otherwise I can look at it later today.

[Josh Tome]

Eventhough neither of the image files have any transparency, I was hoping to eliminate what appears to be the transparency of the top image so that you can't see any of the bottom image through it.

[Image Analyst]

I don't have the code for rotateAround. I'll check back later for it.