Importing SVG into an RMagick RVG session - ruby

We have some code that draws things using RVG in RMagick. We scale them at various sizes. What I'm trying to do is use a file that's saved as an SVG as a template.
The problem is, is when I load an SVG using Magick::Image.read, and then 'use' it, it rasterizes it, and then scales it, instead of producing pretty vectors.
Is there a way one might go about doing this properly?
Thanks!

Thoughts:
Imagemagick is fundamentally raster oriented. If you want to keep your image in vector format, don't use Imagemagick, as the author will tell you. That said, even though imagemagick may by default convert your image to raster, you can convert it back from raster into vector format (sometimes).
SVuGy may help. It doesn't appear to have a lot of support, but may work. I haven't used it.
The rmagick developer claims to have a SVG to RVG parser, you might try contacting him at rmagick AT rubyforge DOT org.
If all else fails, punt. You could write an xslt to convert your svg to rvg. The two formats are close enough that this might not be too painful. Else a tool like genshi might be a faster conversion path for you if you know more python than xlst.

Related

How to create a PNG file with text on it?

From a Ruby app, I need to dynamically create an image file in memory. I'd prefer PNG files so I looked at chunky_png first. It'd allow me to manipulate PNG images and do a little drawing on the canvas. It does not allow me to render text as pixels, though.
What's the best way to do that?
Any hint is greatly appreciated.
You can use RMagick (doc). Note that it may be difficult to install because it requires ImageMagick libraries (unlike chunky_png which is pure Ruby).
Once installed, you may use the annotate method or the vector drawing module RVG (with the text method used in the tutorial).

How can you embed multiple SVG images in a print layout using a scripted procedure?

I currently have a script that produces a large amount of 3.5-inch-square SVG images. What I need is to be able to put these SVGs in a layout which can be easily and accurately printed.
I have tried using an HTML template, but HTML/CSS does not have sufficiently robust printing support.
What document layout language is most appropriate for handling SVG images, and how could this be implemented in a scripting language?
I use Ruby to generate my SVGs, and although preferable, it is not required that Ruby also be the language used to generate the print layout.
I'd suggest compiling all SVGs to a larger SVG, placing everything where you want it, and convert that to PDF using one of multiple options:
Using Inkscape on the command line, like
inkscape -f in.svg -A out.pdf
Using Batik
java -jar batik-rasterizer.jar -m application/pdf -d out.pdf in.svg
Using librsvg, like
rsvg-convert -f pdf -o out.pdf in.svg
(Probably the most lightweight option)
You might also be able to use the rsvg2 Ruby gem with a Cairo PDF surface. Documentation seems scarce or scattered, though.
If you have a budget, Prince is what you want. Since you've already tried to use CSS+HTML to get it working, you may have a working solution almost ready. Just generate the HTML, SVG, and CSS (use the CSS3 paged media extensions for best control), then pass it off to Prince to generate the PDF. I've used this for several projects, and it works great.
There are free options that work like Prince, notably wkhtmltopdf, but they might not respect your paging options as much as Prince.
Otherwise, you might be able to hack something together using Cairo, by creating a page-sized SVG image and laying it out, adding links to the multiple external SVG files.
Either of these options will end up generating a PDF, which is the only way to ensure that it will print the same no matter which browser or OS is being used.

Magento resize with gd2 bad image

i have problems to obtain good thumb from some images, when the original images are striped or checked shirt.
With the magento's gd2 library resize() in Varien_Image_Adapter_Gd2 class (magento 1.5 version) i obtain an image with a strange effect that modify the aspect of real image.
I can't find the name of this effect, so i can't search this issue on google! :(
You can see my issue in these 2 images:
As you can see, on the thumb image there are some rolling strange lines in particular in top-left position.
The issue is more evident on checked shirt, so i have to find a solution to correct this.
If anyone have some tips on this issue, please said me! :)
thx
Luca
'Moire' is the pattern you describe and it is particularly visible due to use of 'gd2' library which may or may not use bicubic scaling.
I am not sure that #Guerra has understood the problem here, but, to me, it is a straightforward lack of bicubic (or better) scaling.
See the answer on this question and follow the link:
https://stackoverflow.com/a/255666/1617149
So you may want to scale your images for the frontend using imagemagick instead of the standard gd2 library that comes with Magento and use a filter.
You can run imagemagick through php (the proper way), or, if you have complicated image processing on the go, you can go commandline 'exec' and prototype your image processing that way. I don't have any ready-to-roll code for that, however, that is what you need: better thumbnail rendering than you get with gd2.
Try use cloudzoom, he autosize your images to fit on your needs.
http://ecommerce-team.com/cloud-zoom.html

Image processing with barehands-ruby

I want to know how to open and manipulate a simple image file in Ruby language.
I don't need to do any advanced stuff, just things like open(), get_pixel() and put_pixel() and I don't wanna use any gem for doing that, but just to know the barehands-ruby way.
If by "simple image file" you refer to JPEG, GIF or so, it's tough luck because you'd have to implement all the decoding logic, which is far from being simple (take a look here for more info, but briefly because you really don't want to go into details ;)).
After decoding, eventually what you get is a matrix (two-dimensional array) of pixel information (usually three numbers for red, green and blue component, but other options exist). Then your methods get_pixel and set_pixel are trivial.
What Ruby folks usually do in such cases is wrap already existing C library for image manipulation, into a library such as rmagick.
Paperclip + ImageMagick did the trick. It's awesome and easy

What is the difference between ImageMagick and libGD?

I don't know anything about either library but I have to choose one of them.
Which one whould you recommend?
I'm using Perl. I need to generate images for weather site. The image is generated for a location and should contain temperature and a weather condition image inside. I guess this is a piece of cake for both libs. But I want to know which one is more powerful. I've read that libGD is not able to rotate text. Maybe there are some other drawbacks? Which one generates images faster? Whose API is easier to use?
according to this source, you should use GD:
GD and other modules built on top of that (like GD::Graph) are more aimed at producing "new" images like charts.
And you can read "Develop your own weather maps and alerts with Perl and GD", which is what you're looking for.
If you some some time. try them both, play a little, and decide.
I find both to be straightforward to use ImageMagick gives you a lot more power than gd. Here are two Magick examples from my posts:
How can I use IO::Scalar with Image::Magick::Read()
How can I resize an image to fit area with Image::Magick?
to give you examples of the API.
I have used GD to create a visualization.
See Script : giss-timeline-graphs.pl on that page.
imagemagick is more robust, however libGD should be able to cover most of the image generation tasks as well. you should see perl API/functions to both of these libraries to see what is more convenient for you.

Resources