I resized an image with scale of 0.25 then upscaled it using scale of 4.
imageReduced = imresize(imageOriginal, 0.25, 'nearest');
imageGenerated = imresize(imageReduced, 4, 'nearest');
I want to calculate mean square error between imageOriginal and imageGenerated so they must have same height x width values. But after downscale and upscale operations image size changes slightly because of the division.
For example;
size of imageOriginal is 4811 x 6449 and
size of imageGenerated is 4812 x 6452
How can I make downscale and upscale operations to make imageGenerated same size with imageOriginal to calculate mean square error between them?
imresize support resize with fixed number of cols and rows: imresize(img, [rows, cols]). You can use this function variant for second resize.
imageReduced = imresize(imageOriginal, 0.25, 'nearest');
imageGenerated = imresize(imageReduced, size(imageOriginal), 'nearest');
Related
I have created a synthetic image that consists of a circle at the centre of a box with the code below.
%# Create a logical image of a circle with image size specified as follows:
imageSizeY = 400;
imageSizeX = 300;
[ygv, xgv] = meshgrid(1:imageSizeY, 1:imageSizeX);
%# Next create a logical mask for the circle with specified radius and center
centerY = imageSizeY/2;
centerX = imageSizeX/2;
radius = 100;
Img = double( (ygv - centerY).^2 + (xgv - centerX).^2 <= radius.^2 );
%# change image labels from double to numeric
for ii = 1:numel(Img)
if Img(ii) == 0
Img(ii) = 2; %change label from 0 to 2
end
end
%# plot image
RI = imref2d(size(Img),[0 size(Img, 2)],[0 size(Img, 1)]);
figure, imshow(Img, RI, [], 'InitialMagnification','fit');
Now, i need to create a rectangular mask (with label == 3, and row/col dimensions: 1 by imageSizeX) across the image from top to bottom and at known angles with the edges of the circle (see attached figure). Also, how can i make the rectangle thicker than 1 by imageSizeX?. As another option, I would love to try having the rectangle stop at say column 350. Lastly, any ideas how I can improve on the resolution? I mean is it possible to keep the image size the same while increasing/decreasing the resolution.
I have no idea how to go about this. Please i need any help/advice/suggestions that i can get. Many thanks!.
You can use the cos function to find the x coordinate with the correct angle phi.
First notice that the angle between the radius that intersects the vertex of phi has angle with the x-axis given by:
and the x coordinate of that vertex is given by
so the mask simply needs to set that row to 3.
Example:
phi = 45; % Desired angle in degrees
width = 350; % Desired width in pixels
height = 50; % Desired height of bar in pixels
theta = pi-phi*pi/180; % The radius angle
x = centerX + round(radius*cos(theta)); % Find the nearest row
x0 = max(1, x-height); % Find where to start the bar
Img(x0:x,1:width)=3;
The resulting image looks like:
Note that the max function is used to deal with the case where the bar thickness would extend beyond the top of the image.
Regarding resolution, the image resolution is determined by the size of the matrix you create. In your example that is (400,300). If you want higher resolution simply increase those numbers. However, if you would like to link the resolution to a higher DPI (Dots per Inch) so there are more pixels in each physical inch you can use the "Export Setup" window in the figure File menu.
Shown here:
I want to apply Temporal Median Filter to a depth map video to ensure temporal consistency and prevent the flickering effect.
Thus, I am trying to apply the filter on all video frames at once by:
First loading all frames,
%%% Read video sequence
numfrm = 5;
infile_name = 'depth_map_1920x1088_80fps.yuv';
width = 1920; %xdim
height = 1088; %ydim
fid_in = fopen(infile_name, 'rb');
[Yd, Ud, Vd] = yuv_import(infile_name,[width, height],numfrm);
fclose(fid_in);
then creating a 3-D depth matrix (height x width x number-of-frames),
%%% Build a stack of images from the video sequence
stack = zeros(height, width, numfrm);
for i=1:numfrm
RGB = yuv2rgb(Yd{i}, Ud{i}, Vd{i});
RGB = RGB(:, :, 1);
stack(:,:,i) = RGB;
end
and finally applying the 1-D median filter along the third direction (time)
temp = medfilt1(stack);
However, for some reason this is not working. When I try to view each frame, I get white images.
frame1 = temp(:,:,1);
imshow(frame1);
Any help would be appreciated!
My guess is that this is actually working but frame1 is of class double and contains values, e.g. between 0 and 255. As imshow represents double images by default on a [0,1] scale, you obtain a white, saturated image.
I would therefore suggest:
caxis auto
after imshow to fix the display problem.
Best,
I'm looking to take in an image of 162x193 pixels and basically scale it down by 0.125 i.e 162/8 = 20.25 and 193/8 = 24.125. Thus I would like a picture of size 20x24 The only problem I'm currently having is that when I use the imresize function it rounds up the images pixel values i.e I get an image of size 21x25 instead of 20x24. Any way of getting 20x24 or is this problem something I'm going to have to live with? Here is some code:
//Read in original Image
imageBig = imread(strcat('train/',files(i).name));
//Resize the image
image = imresize(imageBig,0.125);
disp(size(image));
It appears that with the scale argument being provided, imresize ceils up the dimensions as your results show. So, I guess an obvious choice is to manually provide it the rounded values as dimensions.
Code
%%// Scaling ratio
scale1 = 0.125;
%%// Get scaled up/down version
[M,N,~] = size(imageBig);
image = imresize(imageBig,[round(scale1*M) round(scale1*N)]);
Suppose the current scale of my UIView is x. Suppose I apply a scale transformation to my UIView of the amount y ie:
view.transform = CGAffineTransformScale(view.transform, y, y);
. How do I determine what the value of the scale of the UIView after the scale transformation occurs (in terms of x and y?).
The scale transform multiplies the current scale with your scale y.
if the scale was 2.0 for retina, it is y* 2.0 afterwards.
So x*y is the answer. but dont forget x.achsis scale and y achsis can be different.
x, and y for scale is confusing, better use s1 and s2, or sx, sy if you have different scale on y and x achsis, in your code.
Scaling combines by multiplication, translation (movement) by addition, rotation is a matrix multiplication. All three can be combined into an AffineTransformation (a matrix with 1 more row than the dimensions of the space), these are combined by matrix multiplication. 2D AffineTransformations are 3x2 or 3x3 matrices, the extra column just makes them easier to work with.
Edit:
Using clearer names: if he current scale was currxs, currys and the scale applied was xs,ys the new scale would be currxs*xs, currys*ys. Note that applying a scale will also scale any translation component that is contained in the AffineTransformation, this is why order of application is important.
Its quite simple if you are just using the CGAffineTransformScale and not the other transformations like rotation, you can use the view frame and bounds size to calculate the resulting scale values.
float scaleX = view.frame.size.width/view.bounds.size.width;
float scaleY = view.frame.size.height/view.bounds.size.height;
I want to increase the image size with respect to pixels, that is a image of size 150x225 should be changed to 250x250. How can I do that in Matlab?
You can use the matlab function imresize.
e.g. B = imresize(A, [250 250]);
where A is your initial image with size (150x225).