I have gat some samples about how to open a presentation and access the slides and shapes. But I want to do some more other operations(e.g. generate a thumbnail from a specified slide). What methods can I use? Is there any document illustrating all the functionalities?
Not to discourage you, but my experience using COM from Python is that you won't find many examples.
I would be shocked (but happy to see) if anybody posted a big tutorial or reference using PowerPoint in Python. Probably the best you'll find, which you've probably already found, is this article
However, if you follow along through that article and some of the other Python+COM code around, you start to see the patterns of how VB and C# code converts to Python code using the same interfaces.
Once you understand that, your best source of information is probably the PowerPoint API reference on MSDN.
From looking at the samples Jeremiah pointed to, it looks like you'd start there then do something like this, assuming you wanted to export slide #42:
Slide = Presentation.Slides(42)
Slide.Export FileName, "PNG", 1024, 768
Substitute the full path\filename.ext to the file you want to export to for Filename; string.
Use PNG, JPG, GIF, WMF, EMF, TIF (not always a good idea from PowerPoint), etc; string
The next two numbers are the width and height (in pixels) at which to export the image; VBLong (signed 32-bit (4-byte) numbers ranging in value from -2,147,483,648 to 2,147,483,647)
I've petted pythons but never coded in them; this is my best guess as to syntax. Shouldn't be too much of a stretch to fix any errors.
Related
I have read a lot of essays and articles about (Compressing Image Algorithm). There are many algorithms which I can only understand some of them because I'm a student and I haven't gone to high school yet. I read this article which it helps me a lot! Article In page 3 at this part (Run length code). It's a very EZ and helpful algorithm but I don't know how do I make new format of image. I am a python developer but I don't know how to make a new format which it has a separate algorithm and program. --> like .jpeg, ,jpg, .png, .bmp
(Sorry I have studied English for 1 years so if I have some problems such as grammar or vocabulary just excuse me )
Sure, you can make your own image file format. Choose a filename extension, define how it will be stored and write Python code to:
read the format from disk into a Numpy array, and
write an image contained in a Numpy array to disk
That way you will be interoperable with all the major image processing libraries such as OpenCV, scikit-image, PIL, wand.
Have a look how NetPBM works to get started with a simple format. Maybe look at PCX format if you like the thought of RLE.
Read up on how to write binary to a file with Python.
From my current understanding, png is relatively easier to decode than bitmap-based formats like jpg in python and is already implemented in python elsewhere. For my own purposes though I need the jpg format.
What are good resources for building a jpg library from scratch? At the moment I only wish to support the resizing of images, but this would presumably involve both encoding/decoding ops.
Edit: to make myself more clear: I am hoping that there is a high level design type treat of how to implement a jpg library in code: specifically considerations when encoding/decoding, perhaps even pseudocode. Maybe it doesn't exist, but better to ask and stand on the shoulders of giants rather than reinvent the wheel.
Use PIL, it already has highlevel APIs for image handling.
If you say "I don't want to use PIL" (and remember, there are private/unofficial ports to 3.x) then I would say read the wikipedia article on JPEG, as it will describe the basics, and also links to in depth articles/descriptions of the JPEG format.
Once you read over that, pull up the source code for PIL JPEGS to see what they are doing there (it is surprisingly simple stuff) The only things they import really, are Image, which is a class they made to hold the raw image data.
I would like to be able to convert SVG documents to black and white. My try is the following Makefile script using 'sed' :
%.bw.svg: %.svg
sed '/stroke:none/!s/stroke:[^;\"]*/stroke:black/g' $< > $#
This works for lines etc but not for fillings. Basically if the stroke is not invisible (none), then I convert it to black. I would like to do the same for fillings, if not white or invisible, then convert to black.
I wonder if it would be too complex to do something like this in a better way, perhaps using XSLT, but I have no experience. Anyone can help ?
Two options that I would try:
1- Inkscape appears to be able to do it - Inkscape Convert
2- SVG supports a ColorProfile attribute on the SVG element that can reference an ICC Color Profile. I would try to reference a GrayScale color profile there and see what happens. Looks like there is one available here.
My first thought is that it can be dangerous to manipulate XML (in this case SVG) via sed etc. since it won't escape XML chars properly or respect character encodings.
Having said that, your dataset may be sufficiently constrained and limited such that this isn't a particular problem.
Considering XPath solutions (inc. XSLT) sounds good since you'll be able to precisely identify the components you want to change. Some implementation of XQuery may be of use here.
A very different alternative is XMLStarlet - a command line toolset used for processing XML in scripts.
Finally, can you use a programmatic toolset to do this ? Batik would be my first choice (in the Java world).
I think you need a full CSS parser to do this job for all of SVG; but for "SVG as generated by some particular vector editing application", XSLT containing string editing of the style attributes (as you're doing now, except that it will properly stick to the styles and avoid e.g. <text>) might be adequate.
It would be useful if you'd edit your question to explain how your strategy fails for fill colors.
First of all: Don't try doing this with sed. Editing XML is a little more complex than that.
You can use an SVG filter effect on the image. The ColorMatrix filter primitive can desaturate an image.
I'm not familiar with the PDF specification at all. I was wondering if it's possible to directly manipulate a PDF file so that certain blocks of text that I've identified as important are highlighted in colors of my choice. Language of choice would be python.
It's possible, but not necessarily easy, because the PDF format is so rich. You can find a document describing it in detail here. The first elementary example it gives about how PDFs display text is:
BT
/F13 12 Tf
288 720 Td
(ABC) Tj
ET
BT and ET are commands to begin and end a text object; Tf is a command to use external font resource F13 (which happens to be Helvetica) at size 12; Td is a command to position the cursor at the given coordinates; Tj is a command to write the glyphs for the previous string. The flavor is somewhat "reverse-polish notation"-oid, and indeed quite close to the flavor of Postscript, one of Adobe's other great contributions to typesetting.
The problem is, there is nothing in the PDF specs that says that text that "looks" like it belongs together on the page as displayed must actually "be" together; since precise coordinates can always be given, if the PDF is generated by a sophisticated typography layout system, it might position text precisely, character by character, by coordinates. Reconstructing text in form of words and sentences is therefore not necessarily easy -- it's almost as hard as optical text recognition, except that you are given the characters precisely (well -- almost... some alleged "images" might actually display as characters...;-).
pyPdf is a very simple pure-Python library that's a good starting point for playing around with PDF files. Its "text extraction" function is quite elementary and does nothing but concatenate the arguments of a few text-drawing commands; you'll see that suffices on some docs, and is quite unusable on others, but at least it's a start. As distributed, pyPdf does just about nothing with colors, but with some hacking that could be remedied.
reportlab's powerful Python library is entirely focused on generating new PDFs, not on interpreting or modifying existing ones. At the other extreme, pure Python library pdfminer entirely focusing on parsing PDF files; it does do some clustering to try and reconstruct text in cases in which simpler libraries would be stumped.
I don't know of an existing library that performs the transformational tasks you desire, but it should be feasible to mix and match some of these existing ones to get most of it done... good luck!
Highlight is possible in pdf file using PDF annotations but doing it natively is not that easy job. If any of the mentioned library provide such facility is something that you may look for.
I'm interested in precisely extracting portions of a PCM WAV file, down to the sample level. Most audio modules seem to rely on platform-specific audio libraries. I want to make this cross platform and speed is not an issue, are there any native python audio modules that can do this?
If not, I'll have to interpret the PCM binary. While I'm sure I can dig up the PCM specs fairly easily, and raw formats are easy enough to walk, I've never actually dealt with binary data in Python before. Are there any good resources that explain how to do this? Specifically relating to audio would just be icing.
I read the question and the answers and I feel that I must be missing something completely obvious, because nobody mentioned the following two modules:
audioop: manipulate raw audio data
wave: read and write WAV files
Perhaps I come from a parallel universe and Guido's time machine is actually a space-time machine :)
Should you need example code, feel free to ask.
PS Assuming 48kHz sampling rate, a video frame at 24/1.001==23.976023976… fps is 2002 audio samples long, and at 25fps it's 1920 audio samples long.
I've only written a PCM reader in C++ and Java, but the format itself is fairly simple. A decent description can be found here: http://ccrma.stanford.edu/courses/422/projects/WaveFormat/
Past that you should be able to just read it in (binary file reading, http://www.johnny-lin.com/cdat_tips/tips_fileio/bin_array.html) and just deal with the resulting array. You may need to use some bit shifting to get the alignments correct (https://docs.python.org/reference/expressions.html#shifting-operations) but depending on how you read it in, you might not need to.
All of that said, I'd still lean towards David's approach.
Is it really important that your solution be pure Python, or would you accept something that can work with native audio libraries on various platforms (so it's effectively cross-platform)? There are several examples of the latter at http://wiki.python.org/moin/PythonInMusic
Seems like a combination of open(..., "rb"), struct module, and some details about the wav/riff file format (probably better reference out there) will do the job.
Just curious, what do you intend on doing with the raw sample data?
I was looking this up and I found this: http://www.swharden.com/blog/2009-06-19-reading-pcm-audio-with-python/
It requires Numpy (and matplotlib if you want to graph it)
import numpy
data = numpy.memmap("test.pcm", dtype='h', mode='r')
print "VALUES:",data
Check out the original author's site for more details.