[EDIT]
I am working on a path-following problem where the path is described by the geometric path of letters from a font. Bezier curves will solve my problem of a predefined geometric path in terms of an equation, but I can't seem to find a tool that enables me to generate Bezier curves of each letter from a font, with a weight of 0. The figure below illustrates what I want to achieve.
Weighted 'a' to non-weighted 'a':
The path-following problem that I need to solve will be present in a robot with a control system (Constrained Model Predictive Control for non-linear path-following) that will write these letters with a pen. I simply need a tool that could extract a Bezier curve(s) from each letter of an existing font. Fontforge (windows) shows the Bezier curve control points from where an outline of a glyph is constructed. The problem with Fontforge is that fonts are defined to have some sort of "thickness", which in turn results in a need to fill the character. My robot should only write the letters like a human would do (no-filling). A partial solution to this problem will also help.
Note: I am not sure whether this is possible using Fontforge (Windows), and changing the weight attribute of a glyph gives errors.
Reference to a similar robot: Bond│ HANDWRITING│ writing robot.
Related
this is the first I'm working with PDFs on this level. So please be patient with
my noob question. I understand the logical and physical structure of an PDF file
on a basic level.
I have an PDF that contains a dummy ID that needs to be replaced. To check, if there
is way to do this, I used qpdf to expand the PDF using
qpdf --qdf --object-streams=disable orig.pdf expanded.pdf
Using a hex editor I located the dummy ID in expanded.pdf and changed the value by
simply swapping two digits
<001800180017> Tj => <001700170018> Tj
and saved it. Opening expanded.pdf in Acrobat didn't show the modification. The original
ID 443 is still rendered, but searching for "443" doesn't find it. When searching for
"334", the modified content, I get the rendered original ID 443 highlighted.
The PDF consist of text and vector graphic. When I insert additional digits (which obviously
invalidates the offsets in the xref), I get an error message regarding a missing font and
all digits are shown as dots but the vector graphic is still in place. This seems to indicate
that the ID is not part of the graphic.
What did I miss?
EDIT 1:
After mkl's comment, I did a deeper analysis of my PDF and found, that beside the obvious graphic content, all text was rendered by a series of m/l/c commands follwoed by a BT/ET section. Color for stroke and non-stroke was 0,0,0 for both in the BT/ET section.
Is this because of the used embedded non-standard font?
Are PDFs with embedded fonts usually done this way? A graphics part for the visual representation and a transparent (hidden) text part just to get searching and highlighting capabilities?
Looking back I wonder what I did to get the dots when I first modified the
content. I seems impossible and I can't reproduce it either.
Thanks
Tom
First off, the following is merely guesswork as you could not share the pdf in question. Educated guesswork but guesswork nonetheless.
You report that you changed the value by simply swapping two digits in the text drawing instruction argument and now can successfully search for the value with swapped digits but that Acrobat didn't show the modification.
Furthermore you observed that all text was rendered by a series of m/l/c commands followed by a BT/ET section.
The main situation in which one observes text being rendered as arbitrary vector graphics (a series of m/l/c commands), is in pdfs in which the producer didn't want text extraction to be possible and replaced text drawing instructions by arbitrary vector graphics instructions.
This apparently is not the case in your pdf as the text drawing instructions are not replaced but merely supplemented by the vector graphics ones.
Supposing that this construct is used for a reason and not by accident, I can only assume that the pdf producer was not willing or allowed to embed the font in question but wanted the specific font appearance to be displayed without having to count on the font being installed on the computer the pdf is viewed on.
Thus, the text appearance is drawn using arbitrary vector graphics instructions and the following text drawing instructions actually draw nothing but merely make the text searchable and extractable. This way there is no need to embed the apparent font face as font program. (Text drawing instructions can be made to draw nothing either by using a font with all blank glyphs or by using the text rendering mode "invisible".)
If this assumption turns out to be correct, your task to replace the dummy id requires not merely editing the arguments of the text drawing instructions but also replacing the arbitrary vector graphics instructions showing the dummy id appearance by other instructions showing the actual id.
If you happen to have the font in question and are willing and able to embed it, you can actually replace the arbitrary vector graphics instructions by text drawing instructions using the font. Otherwise be prepared to also draw the actual id as arbitrary vector graphics.
I have an excel file containing AutoCAD line data that I wish to map to AnyLogic Path constructs. To do this I am trying to edit the XML file and adding in path objects with the requisite points. The AutoCAD data I have provides a center x,y, start x,y, end x,y, and angle for arc segments, and the standard points for lines. I can't seem to figure out how anylogic draws paths, though. I do not believe they are Bezier Curves, because every path contains 5 points as far as I can tell. For the straight line segments, it's easy enough to map, but for curves I cannot equate my Autocad ARC data with the Anylogic Path construct because I don't actually know how AnyLogic Paths are represented internally.
I tried a Bezier Curve which did not work. Tried adding in the center point of the arc segment as the fourth point but this did not work. Looked at B-Splines, doesn't seem to be this either.
Format examples from AnyLogic
To give more information about thow AnyLogic stores path information internally, here are some examples of the conversion the other way round, from the AnyLogic editor to the AnyLogic XML source file. There are (poly-) lines drawn in the AnyLogic editor and the coordinates of the corresponding end points in the AnyLogic point table and finally the respective XML AnyLogic source file representing the same line.
A simple straight line:
A more complex line:
Another line. The orange arrows show the connection between the visible points and the resulting XML:
I have a pdf which contains many fonts and What is the best way to check whether it contains font that belongs to Arial font family ?
Is this possible in any language?
I couldn't find any library or language that could do this.
So, I tried by converting pdf to image using ImageMagick and segmented all alphabets present in the image(pdf).And then I tried to compare all segmented alphabets to segmented images of arial font family alphabets which worked fine.
I created all datasets using MS Word.But arial font family looks different in different editors.By 'looks different', I mean the segmented image of same alphabet has different pixel values in different editors.And also alphabet of 10pt size has different dimensions in different editors.So, this method doesn't work.
Any Suggestions on how to do this? May be using svg file or ps file
I also came to learn that, In pdf's alphabets are rendered using Bezier curves, where each bezier curve is drawn using some control points and nodes.
Are these control points, same for all alphabets that belong to one font family? If Yes, how to extract control points of alphabets in pdf as these can be used to detect font family.
There can be three types of text in your document:
text that isn't real text, but part of a raster image,
vector text drawn by PDF syntax without using a real font,
vector text using a real font.
The answer to your question depends on the type of text you're confronted with:
There is no way to extract font information if the text is not real text, but part of a raster image. You need an OCR tool to convert the pixels into characters, but you won't get any info about the font family. You could try to compare pixels, but you've already tried that and you've discovered that this isn't trivial (one might consider your current solution as a bad workaround / bad design).
You describe text that is drawn on a page using Bézier curves. Although, it's possible to draw text like this, you won't find many PDFs that are drawn like this. The reason is obvious: every time you'd need a specific glyph, let's say A, you would need to add the syntax to draw that glyph on the page, leading to plenty of redundant PDF syntax.
PDFs usually work with fonts. A font is stored in a PDF file using a font dictionary. The syntax that makes up a page refers to that font using a name that can be chosen by the PDF producer, but that corresponds with an entry in the page resources that contains a reference to the font dictionary. Each font has an encoding mapping characters to glyphs. In the page content we use characters, based on these characters, glyphs will be selected in the font.
You are asking about the font family. This information is stored in the font dictionary. Take a look at my answer to the question What are the ways of checking if piece of text in PDF documernt is bold using iTextSharp and you'll get an idea of what such a font dictionary looks like.
Do you see the /BaseFont entry in the font dictionary? It has values such as JOJJAH+TT116t00. In this case, the name of the font is "TT116t00", but what is "JOJJAH"? That is explained in my answer to the question What are the extra characters in the font name of my PDF?
Not all fonts are embedded. Sometimes the name of the font is sufficient for the viewer to know what the glyphs look like. For instance: there are 14 Standard Type 1 fonts that every viewer should be able to render.
Arial isn't one of those fonts, so if you want to be sure that Arial is rendered correctly, that font needs to be embedded. The font dictionary will refer to a Font Descriptor where you'll find the syntax to draw glyphs using linear paths, Bézier curves, etc. Suppose that you need the character A, then the font descriptor will contain some syntax that knows how to draw that character. The font dictionary will also have a map that maps the character A to the glyph A. Now when you need that glyph in your content, you can just use the character A and that will refer to the syntax that draws the glyph A. That syntax is stored inside the PDF only once.
Suppose that a PDF has the full Arial font embedded, then the value of /BaseFont would be Arial. However, if we'd embed the full Arial font, the PDF would be bloated. There are way too many characters in Arial; we don't need them all. That's why we'll only embed one or more subsets. When you see 6 characters followed by a + sign in the /BaseFont entry, you have discovered a font subset.
Getting the /BaseFont entry of a font dictionary can be done using different libraries. On the official iText site, we have different Q&As that explain how to Inspect a PDF. There's also an example that lists the fonts used in a PDF. Maybe that can be helpful.
NOTE: as explained in the help section, more specifically on the page What topics can I ask about here?, you will find rule #4: Questions asking us to recommend or find a book, tool, software library, tutorial or other off-site resource are off-topic for Stack Overflow as they tend to attract opinionated answers and spam.
I have given you the general information about where to find font information inside a PDF, but it's not allowed for you to ask questions to recommend the best tool to do this. Sorry for that.
I am looking for a way to measure the coordinates of different rectangles on a PDF file?
Mainly I do have to perform some overprinting on an existing PDF and I need to know the x,y,w,h on where I am supposed to write the texts.
It seems that Preview.app on Mac has this ability but so far I wasn't able to find anything on Windows that does the same.
Please do not confuse this feature with the Measuring Tools from Adobe Reader which are used to measure distance in printed construction stuff, not the PDF page itself.
It seems that the default using of measure is point, so I need something that would allow to select a rectangle and that will tell me the coordinates.
Please do not suggest on exporting as a imagine and using something else to measure the pixels on the image.
Update: http://legacy.activepdf.com/support/knowledgebase/view.cfm?tk=rl&kb=11866 -- PDF Units, that's what I am looking for, something to measure the PDF coordinates in PDF units.
Disclaimer: I work for Atalasoft.
I know you said not to suggest this, but honestly, it's the easiest approach:
If you mean "sweep out a rectangle in the UI and report the coordinates", that's pretty straight forward, but it's going to be a build-your-own type of thing. What you will need are:
A PDF rasterizer (GhostScript, Acrobat, FoxIt, Atalasoft) to get you an image at a specific resolution.
A tool to display that image in a window and let you sweep out a rectangle (this is straight forward winforms type code for .NET, but we have a control that does this out of the box - combining 1 & 2 into one step).
A tool that can look at the structure of a PDF page and report back the crop box (if any) and the media box for each page (iText, DotPdf).
A tool/understanding of matrix transformations to build the matrix that goes from display space into PDF space (and/or vice versa, probably in iText, definitely in DotPdf)
The code flow becomes something like:
For each page:
Open document, pull out crop and media box, rasterize page, build transformation matrix.
Display image, build/hook into event for selection changing.
Push the image viewer rectangle coordinates through the transformation matrix.
Profit.
From a coding point of view (assuming 0 prior knowledge of this, but a decent understanding of linear algebra), from 3 days to a 2 weeks. If I were to write it, it would probably take on the order of a few hours, but I wrote most of our PDF tools and this is pretty easy.
If your goal is to intuit where rectangles are on the page and report back those coordinates, that's also doable, but it decidedly non-trivial in comparison. You need to write code that can rip through a PDF display list and interpret the contents correctly. That means being able to handle all the cumulative matrix transformations, the graphics state changes, the gstate object use, Form XObject placement, and so on. You need to answer the question "what is a rectangle?" because in PDF placement, it could be an re operator, a set of degenerate beziers, a set of lines, an image of a rectangle or (surprise!) a combination of all of the above. Honestly, intuiting anything about the content on a PDF page is a Herculean task.
I'm looking for any kind of technology that will let me draw dashed curves in 3D (see attachment) and export it into PDF with a guarantee that dashed lines are still paths in PDF file (not a collection of single little lines!).
I tried Processing, but see no option there to export it correctly.
In theory you can do this if you have the set of Beziers that describe each line and then set set the dash pattern for the line. The dash pattern will be non-uniform and specified to cover the entire length of each path.
The problem I think you will run into is that line thickness cannot vary over the length of a single path, so you can't really get the effect of perspective in the change of line thickness.
How to do this without line thickness change - project the 3D path of each curve onto 2D, measure the projected dash and gap lengths and construct the corresponding PDF path.