I'm starting to use IDL because I want to use some analysis tools for videos that I have found on internet (https://physics.nyu.edu/~fcc4/HVM_site/HVM/software.html), I already have installed IDL package and works properly... When I load my image in PNG format I got
IDL> a=read_image('Imag1.png')
IDL> help, a
A BYTE =Array[3,424,382]
The point is that the routine that I want to use need two dimensional float array that came from an image save as two dimensional byte array. Why is this a three dimensional array? Is it due to the RGB that png format use? Can I converge it to a two dimensional and don't lost the information? The tutorial use uncompressed tif, is the some free tool like VirtualDub which split videos with this format?
This is the image that I load in the code above
Related
Our office does scanning of data entry forms, and we lack any proprietary software that is able to do automated double-entry (primary entry is done by hand, of course). We are hoping to provide a tool for researchers to highlight regions on forms and use scanned versions to determine what participant entry was.
To do this, all I need for a very rough attempt is a file to read in PDFs as raster files, with coordinates as X, Y components, and B&W white "intensities" as a Z-axis.
We use R mainly for statistical analysis and data management, so options in R would be great.
You could use the raster package from R. However, it doesnt support .pdf files, but .tif,.jpg,.png (among many others).
But coverting your pdfs into pngs shouldn't be a big problem: Look here for more information.
Once you have your png files ready, you can do the following:
png <- raster("your/png/file.png")
and then use the extract() function to get your brigthness value from the picture. I.e. let's say your png is 200x200px and you want to extract a pixel value from row 100 and column 150:
value <- extract(png, c(150,100))
In my research work, when papers are to be communicated, the format could be either LaTeX or DOC/DOCX. This sends me into a dilemma.
I have generated PDFs (they can be easily included into a latex file) for certain plots using the base plot method. However, I would also like to have the PNG versions of the same plots (since MS Word does not accepts PDFs), and no, I do not want to rewrite codes! Further, the convert utility of ImageMagick is also not a preferable option, as there is a severe degradation in terms of resolution when one executes convert myFile.pdf myFile.png
What is the best way? Can we save a plot into a variable and then regenerate the plot to a png / jpg / tiff file?
Save to EPS format (see HowTo here). It is a vector format, and it should be recognizable by MS Word (you will need to import it as a picture) as well as LaTeX.
Suppose that I have a PostScript file containing a plot which was generated using gnuplot. However, I do not have the source data, nor do I have the gnuplot commands that were used to generate the plot.
Do you know of any way to somehow extract data from a graphic representation (i.e., a PostScript file)? Such code would have to literally "read off of the graph" (in particular, I have a smoothed line/scatter XY plot) from the pixel representation, and I know that the results would be approximate at best (but this would still be very highly desirable).
Do you have any experience with this? Thank you for your time!
PostScript is nothing but a programming language to describe pages. A PostScript file is a plain text file containing a program that descbrise a page which gets interpreted by a printer or viewer.
As such it is amendable to programmatic manipulation, albeit in a low-level way.
I would approach this task in the following way.
Learn PostScript. (The reference manual will come in handy.)
Study the output from gnuplot. How does the gnuplot outputs the graph? Is this systematic? etcetera.
Parse and extract the needed information.
g3data, available here, looks like a possibility. It runs on Linux.
i am plotting some data in R using the following commands:
jj = ts(read.table("overlap.txt"))
pdf(file = "plot.pdf")
plot(jj, ylab="", main="")
dev.off()
The result looks like this:
The problem I have is that the pdf file that I get is quite big (25Mb). Is the a way to reduce the file size? JPEG is not an option because I need a vector graphic.
Take a look at tools::compactPDF - you need to have either qpdf or ghostscript installed, but it can make a huge difference to pdf file size.
If reading a PDF file from disk, there are 3 options for GostScript quality (gs_quality), as indicated in the R help file:
printer (300dpi)
ebook (150dpi)
screen (72dpi)
The default is none. For example to convert all PDFs in folder mypdfs/ to ebook quality, use the command
tools::compactPDF('mypdfs/', gs_quality='ebook')
You're drawing a LOT of lines or points. Vector image formats such as pdf, ps, eps, svg, etc. maintain logical information about all of those points, lines, or other items that increase complexity, which translates to size and drawing time, as the number of points increases. Generally vector images are the best in a number of ways, most compact, scale best, and highest quality reproduction. But, if the number of graphical elements becomes very large then it's often best to go to a raster image format such as png. When you switch to raster it's best to have a good idea what size image you want, both in pixels and also in things like print measurements, in order to produce the best image.
For information from the other direction, too large a raster image, see this answer.
One way of reducing the file size is to reduce the number of values that you have. Assuming you have a dataframe called df:
# take sample of data from dataframe
sampleNo = 10000
sampleData <- df[sample(nrow(df), sampleNo), ]
I think the only other alternative within R is to produce a non-vector. Outside of R you could use Acrobat Professional (which is not free) to optimize the pdf. This can reduce the file size enormously.
Which version of R are you using? In R 2.14.0, pdf() has an argument compress to support compression. I'm not sure how much it can help you, but there are also other tools to compress PDF files such as Pdftk and qpdf. I have two wrappers for them in the animation package, but you may want to use command line directly.
Hard to tell without seeing what the plot looks like - post a screenshot?
I suspect its a lot of very detailed lines and most of the information probably isn't visible - lots of things overlapping or very very small detail. Try thinning your data in one dimension or another. I doubt you'll lose visible information.
I am using QPainter to draw some graphs on the screen and save these graphs as a raster images.
Is it possible to use the same logic I used for rasterizing these graphs to have them exported to vector images that I can use in a PDF?
You can use a QSvgGenerator as a "backend" to your QPainter, and you'll get an SVG document out of it. (The documentation has an example for how to do that.)
I don't know if you can use that directly in PDFs, but there are converters out there if you need a different vector graphics format.