Apologies if this is a dupe, I've been searching for over an hour but the search terms are all really broad and I just keep getting the same results. Also I'm fairly new to matlab so apologies for any misunderstandings.
Anywho, I have a matlab program which needs to frequently save an image generated from a matrix, but I just can't figure out how to do that without displaying it first. Basically I'm caught in between two functions, image and imwrite, both only do half of what I want.
image is able to take my matrix and create the desired output, but it just displays it to a figure window
imwrite is able to save an image to a file without displaying it, but the image is completely wrong and I can't find any parameters that would fix it.
Other questions I've seen deal with using imread and managing figures and stuff, but I'm just doing (for example)
matrix = rand(20);
colormap(winter);
image(matrix, 'CDataMapping', 'scaled');
or
matrix = rand(20);
imwrite(matrix, winter(256), 'filename.png');
Is there some way to call the image function such that it doesn't display a figure window and then gets saved to a file? Something analogous to calling imshow and then savefig in matplotlib.
Just do this:
matrix = rand(20);
f = figure('visible', 'off');
colormap(winter);
image(matrix, 'CDataMapping', 'scaled');
print(f, '-dpng', 'filename.png');
Related
I'm working with fastai, trying to pass some images to a dataloader. The original images are kind of pinkish, but after passing them they appear mostly as green-black (see image in link below):
Original pinkish image (up) and example images (down) after passing them to dataloader, and the code.
The code I've used for the datablock and to show the images is:
example = DataBlock(
blocks=(ImageBlock, CategoryBlock),
get_items=get_image_files,
splitter=GrandparentSplitter(),
get_y=parent_label,
item_tfms=Resize(128)) #already tried it without item_tfms just in case, still black-green
dls = example.dataloaders(path)
dls.show_batch(nrows=1, ncols=3)
I tried with .tif and .jpeg images, and both show the same problem. The only thing that comes to my mind is that somewhat somewhere is not reading correctly the color format (RGB according to my original files), or maybe transforming it; but I'm not able to figure it out.
Just in case it's important, I'm working in a Jupyter notebook with a MackBook Air M1.
Thanks!
Irene
I'm using the print function in MATLAB to write images of plots, something like that
print(figure(1),'-dpng','-r300',filename);
But apparently the images are not overwritten, and the original images stay. I was using saveas before, which seems to overwrite the images, but print gives me more output options. Any ideas?
UPDATE: I ended up deleting the files before the printing with a different function.
You can use this:
im = frame2im(getframe(gcf,rec)); %Grabs image of plot as an image
imsave(im, filename); %save image
That syntax may not be 100%, its a while since I've used it.
Also be aware that this isn't perfect - I remember having issues with it grabbing a grey border around the edge of the plot. Also, I think the image may be based on a matlab screenshot.... just something to be aware of
Saving figures in matlab is rather troublesome, especially if the saved image should look like the original figure.
For myself i found the solution in using export_fig.
It's one of the most downloaded fileexchange files - maybe you should give it a try:
http://www.mathworks.de/matlabcentral/fileexchange/23629-export-fig
A small introduction to export_fig can be found at:
https://github.com/ojwoodford/export_fig/blob/master/README.md
can anyone help me to save my resulted images by using imwrite
source = 'C:\Y\';
im_number=5;
for i=1:5
image{i}=im2double(imread([source,'Carbon_', num2str(i)],'tif'));
image{i}=double(image{i});
B{i}= Sftfun(image{i});
B{i}=uint32(B{i});
imwrite(B{i},[source,'face_', num2str(i)],'tif');
end
The problem with your code is that you are casting your image to uint32. If you are trying to save your image as a TIF file, you can only save it as 8-bit or 16-bit. Consulting the MATLAB documentation, you can only save with these two bit depths. 32-bit depths are not supported.
Consult the MATLAB documentation for more details: http://www.mathworks.com/help/matlab/ref/imwrite.html
As such, either cast the image as 8-bit or 16-bit (through im2uint8 or im2uint16), or normalize your image so that it goes from [0,1] (through im2double).
I also have some comments about your code that do need fixing for readability:
Do not save your images to a cell array called image. MATLAB has a built-in command called image which takes in a matrix and displays it to the screen for you as an image. Bear in mind this is not the same as imshow. By doing this assignment, you will shadow over the actual image command, and so any scripts that rely on this function will result in an error.
im_number seems to be an unused variable. I'm not sure what its purpose is, but I'd say it's safe to remove this statement as well.
Get rid of the following statement as you are already converting the image to a double type in the previous line:
image{i} = double(image{i});
Aside
It seems that you have asked a similar question here: save tif 32 bit images by using imwrite
This question has already been resolved in that you are not able to save 32-bit images using imwrite. However, someone in this thread has posted a workaround for you to use in MATLAB. Try using that instead of imwrite.
I am using R to plot trying to conditionally change parts of an array
based on the columns of the array.
I have worked out the following steps:
x<-array(1,dim=c(4,4,3))
r<-x[,,1]
g<-x[,,2]
b<-x[,,3]
r1<-apply(r[,2:3],1:2,function(f){return(0)})
g1<-apply(g[,2:3],1:2,function(f){return(0)})
b1<-apply(b[,2:3],1:2,function(f){return(0)})
r3<-cbind(r[,1],r1,r[,4])
g3<-cbind(g[,1],g1,g[,4])
b3<-cbind(b[,1],b1,b[,4])
# Pass to pixmapRGB
This works, but as I am new to R, I was wondering if
there was a more efficient way to manipulate parts
of an array.
For example, does apply know which element it is working on?
The bigger picture is that I want to graph a time-series scatter
plot over many pages.
I would like to have a thumbnail in the corner of the page that is
a graph of the whole series. I would like to color a portion of
that thumbnail a different color to indicate what range the
current page is examining.
There is alot of data, so it is not feasible to redraw a new plot
for the thumbnail on every page.
What I have done is to first write the thumbnail plot out to a tiff file.
Then I read the tiff file back in, used getChannels from pixmap
to break the picture into arrays, and used the above code to change
some of the pixels based on column.
Finally I then print the image to a viewport using
pixmapRGB/pixmapGrob/grid.draw
It seems like alot of steps. I would be grateful for any pointers
that would help me make this more efficient.
Maybe I don't understand your question, but if what you're trying to do is just "change some pixels based on column," why don't you just use the basic array indexing to do that?
This will do the same thing you have posted:
x<-array(1,dim=c(4,4,3))
r<-x[,,1]
g<-x[,,2]
b<-x[,,3]
r[,2:3]=0
g[,2:3]=0
b[,2:3]=0
Is that helpful?
Perhaps more of a comment than an answer, but when I try to plot over a number of pages I usually go left to right, breaking up the plots into quantiles and setting appropriate xlim (or ylim)
x <- rnorm(100000)
y <- rnorm(100000)
df <- data.frame(x,y)
seq1 <- quantile(df$x, probs = seq(0,1,0.1))
seq2 <- quantile(df$x, probs = seq(0,1,0.1))
for(x in 1:(length(seq1)-1)) {
plot(df, xlim=c(seq1[x],seq1[x+1]))
}
No idea how to overlay a thumbnail onto the graphs although I think you could do this with one of the rimage functions if you saved the thumbnail.
You could avoid having to read and paste a tiff thumbnail by actually replotting the whole chart at reduced scale. check out par(fig) , and then do something like
Rgames: plot(1:2,1:2)
Rgames: par(mar=c(.1,6,.1,.1),new=T,fig=c(0,.25,.5,.75))
Rgames: plot(1:2,1:2)
Rgames: polygon(c(1,2,2,1),c(1,1,2,2),col='red')
("Rgames:" is my prompt)
You'll have to play a bit with the margin values, but this will get your "mini-graph" set up.
I need to plot and display several jpeg images in a single combined display (or canvas?). For example, suppose I have images {a,b,c,d}.jpg, each of different size, and I would like to plot them on one page in a 2x2 grid. It would be also nice to be able to set a title for each subplot.
I've been thoroughly looking for a solution, but couldn't find out how to do it, so any ideas would really help. I would preferably use a solution that is based on the EBImage package.
There are two ways how to arrange several plots with base graph functions, namely par(mfrow=c(rows,columns)) (substitute rows and columns with integers) and layout(mat) where mat is a matrix like matrix(c(1,2,3,4)).
For further info see ?par, ?layout, and especially Quick-R: Combining Plots.
However, as your question is about images I don't know if it helps you at all. If not, I am sorry for misinterpreting your question.
To add to Henriks solution, a rather convenient way of using the par() function is:
jpeg(filename="somefile.jpg")
op <- par(mfrow=c(2,2)
#plot the plots you want
par(op)
dev.off()
This way, you put the parameters back to the old state after you ran the code. Be aware of the fact this is NOT true if one of the plots gave an error.
Be aware of the fact that R always put the plots in the same order. Using mfrow fills the grid row by row. If you use mfcol instead of mfrow in the code, you fill up column by column.
Layout is a whole different story. Here you can define in which order the plots have to be placed. So layout(matrix(1:4,nrow=2) does the same as par(mfcol=c(2,2)). But layout(matrix(c(1,4,3,2),ncol=2)) places the first plot lefttop, the next one rightbottom, the third one righttop, and the last one leftbottom.
Every plot is completely independent, so the titles you specify using the option main are printed as well. If you want to have more flexibility, you should take a look at lattice plots.
If you do not want the images in a regular grid (the different sizes could imply this), then you might consider using the subplot function from the TeachingDemos package. The last example in the help page shows using an image as a plotting character, just modify to use your different images and sizes/locations.
The ms.image function (same package) used with my.symbols is another possibility.