I just started at a new company and have been asked to do what I believe impossible, but I need confirmation on this. The website that my company has allows users to view images in extremely high resolution using SVGs. We've built a custom viewer for these images that allow you to zoom and scroll around the image and it works well. Because of this, the image format "needs" to remain SVG. However, we need to include a watermark to this image. The way we're doing this right now is passing the SVG and PNG watermark to the client, inserting the watermark into the SVG, and displaying it to the user. This is very obviously easily hacked as anyone with client-side experience knows (The dev team here is mostly older developers and don't have much web experience). Even if the raw SVG isn't intercepted, they can still just delete the watermark from the source. I've convinced my boss to make the watermark be injected on the server-side, so this leaves just the problem that SVGs are editable by the end-client.
What I want to know is if one of these two things are possible:
1) Is there another image format akin to SVG that could be used to keep this highly scalable image without loosing resolution, and without it being directly editable by an end-client? The only options that people seem to discuss for the web is JPG, GIF, PNG, and SVG. I've looked at Adobe Illustrator ".ai" files and EPS (Encapsulated PostScript) as other vector options, but I can't find anywhere if I can modify these images in PHP, which is key if I want to overlay a watermark in server-side code.
2) Is there a way to obfuscate the raw SVGs content so that the use can't go and manipulate it? I've seen SVGs that have <image ...> tags inside them with PNGs represented as long and complex strings before. Something like xlink:href="data:image/png;base64...". I was wondering if there's a way to display an SVG as this string, so that the data can't be directly manipulated. I'm sure there's an algorithm to reverse these, but so long as we're sticking with SVGs, I need to make this as secure as possible with as many hoops to jump through as possible if someone wants to steal the data.
Either way would be acceptable, as long as removing this watermark is more complex than just hitting F12 and removing the element inside the dev tools.
Is there another image format akin to SVG that could be used to keep this highly scalable image without loosing resolution, and without it being directly editable by an end-client?
SVG is a vector format, and to maintain extreme scalability, you need to stick with vectors, be it any format. However, in that case it will always be possible to remove the vectors that belong to your watermark. There are of course vector formats that are stored as binary, which would make it somewhat harder for an enduser to parse and edit, but those are not editable in PHP either, and are much less compatible. So you probably don't want to do this.
Is there a way to obfuscate the raw SVGs content so that the user can't go and manipulate it?
First, it will never be "secure" in the sense that as said above, it will always be possible to remove the watermark from a vector image. (Btw the only difference to bitmap formats like JPG is that content below the watermark in bitmap is actually missing, while in SVG it's still there.)
However, depending on how "good" you want this to be, you can do a few things. I think the "goodness" here means the effort needed to remove the watermark, and you can raise the bar relatively easily. You don't have to (and you probably can't reasonably) obfuscate the whole SVG.
One thing that comes to mind is that SVG is basically just XML, it consists of tags like <rect>, <line>, <circle> etc. The order of these tags doesn't matter much (mostly, with exceptions of course). So you could entwine the tags that draw your watermark pretty much randomly among existing tags. I mean really randomly, so different downloads would produce different results. If you do this well (eg. you find line tags to "hide" your watermark line tags, and so on), it will be hard to automatically remove the watermark, because it's all over relevant data that is your actual image. Of course, the watermark could still be visually in a corner, and this is already a weakness, anything drawn to a corner could possibly be removed automatically. And it will be easy to remove by hand with any decent editor I suppose. So it depends on what the purpose is.
But I still think this sort of thing could make it hard enough in many scenarios (and would be totally inadequate in others).
Related
I am looking for the best approach for generating images of text on the server side (preferably Node.js). It will need to accommodate things like paging (so generating multiple images of text for one text input if it is too long to fit on one page). I am looking for something that is fairly precise and allows for a good deal of type configuration.
I have looked at a few options:
Use Canvas. This approach would work for most of the use cases. I could use a text engine like textjs for the layout. However, this is somewhat limiting as Canvas doesn't have specific text metrics (for things like text height used for exact positioning). This could make paging difficult.
Use normal HTML with something like PhantomJS to generate and them capture an image of the text. While this approach will work for some use cases, it makes it hard to handle things like paging.
Use some other text engine. I've looked around and found some options - but it would need to be something that I could call from Nodejs (as I'll likely use this on AWS Lambda).
What would you recommend?
I lately did something very similar - also with node.js on Lambda. In my opinion the best approach is using PhantomJS and maybe taking the detour of generating a PDF.
With HTML and CSS you can conveniently style the output exactly how you want it, which is a great advantage about the way more complicated Canvas approach. You only have to take care of adding some horizontal space wherever you expect the pagebreak (of course this depends on your usecase and may not be necessary). Having the rendered HTML page you now have two options:
You could generate a PDF - which will take care of generating multiple pages - and then rasterize that to images
Or you directly generate an image with Screen Capture (example Code) and then splitt that image horizontally
Both approaches worked fine for me.
I have to draw charts on browser using a python backend (which may not matter here). There are numerous libraries like JQPlot, D3, Google Charts for achieving this.
But if you classify them, they are either HTML5 Canvas based or SVG based. Both are important technologies in their own space. But
for charting as a subject, shall I go with SVG based libraries or
HTML5 Canvas based libraries. What are downside and benefits of
both approaches.
I don't have any prior experience with charting and don't want to hit the wall
after I start the project.
Projects with a large amount of data may favor canvas. SVG approaches typically create a DOM node per point (unless you make paths), which can lead to:
An explosion in the size of your DOM tree
Performance problems
Using a path, you can get around this problem, but then you lose interactivity.
Say you're building a stock chart. If you are talking about a chart with, say... max 5 years and end of trade data samples only, I think the answer is clearly SVG. If you're talking about looking at Walmart's historical data from day one of trading or doing full trade information per minute, you are going to have to really look carefully at SVG. Probably will have to employ fancy memory management and a fetch-on-demand approach as SVG will fall apart, particularly if you go one sample to one SVG node.
If interactivity is a requirement, SVG easily has the edge, given:
It is a retained mode API
You can use typical event handlers
You can add/remove nodes easily, etc.
Of course, you see that if you require full interactivity, it may go against mechanisms that allow SVG to scale, like path collapsing, so there is an inherent tension here.
There is going to be a trade-off in extremes. If size is small, the answer is SVG hands-down. If size is large and no interactivity, the answer is SVG with path drawing only or using Canvas. If size is large and interactivity is required, you have to go canvas or tricky SVG, which is complex in either case.
Some libraries out there offer both canvas and SVG renders, such as ZingChart and Dojo. Others tend to stick with just one of the two options.
Being vector based, SVG gets you scalability for free, and a side effect of this is that it's sharp on high resolution displays and sharp when printed. You can kind of get around this with canvas by rendering at 2x resolution and scaling your canvas but it's kind of a half-solution.
SVG I think is the modern way and the way to do this moving forward.
If you are concerned about rendering speed if you have many nodes consider also that if you're using canvas, you're basically using your own Javascript based rendering code which has to render those same nodes. You do get the predictability of only having to render it once, but if you only render it once that also means you lose the ability to re-render when zooming or to do various interactive things. If performance is a problem you can simplify SVG by sub-sampling your data, taking moving averages and plotting that only once per x rows, etc depending on what you're doing. But, we're talking thousands and thousands of nodes with almost no impact.
Canvas still has a place if you are building a web based raster graphics editor or something that in inherently raster-based but essentially if we are looking at charts, we're talking about something that's inherently vector based.
I'm putting together a mobile version of a webpage which consists entirely of client art. For the old-fashioned desktop version, I just used PNGs, but I really wanted to use SVG for mobile. SVGZ would be smaller and resolution independent, so it seemed like a perfect use case.
But the client is worried that, once his art is online in SVG, anyone could download the files and use his art illegally (he's had stuff he worked on pirated before, so he takes this pretty seriously.) This had never occurred to me until he brought it up, but the SVG would basically be his original source art.
I was wondering if there's any way to prevent the SVG files from being accessed by the user. As far I know this is impossible -- making the files available to the user-agent means making them available to the user -- but I wanted to ask around to be sure.
Thanks for any help.
No, this is impossible. If a web browser can request the files for display, then any computer anywhere can request the files and save the direct results.
Serving up intentionally degraded artwork (e.g. rasterization) is the only way to prevent people from having the originals. Of course, a determined thief could still re-trace the PNG and get a vectorized, resolution-independent close approximation of the original.
Your client could alternatively:
Include copyright comments in the source, proving ownership. (Yes, a thief could delete these.)
Include 'hidden' elements (0% opacity or placed under another item), proving ownership. (Yes, a thief could delete these.)
Use data steganography in the source SVG to watermark it (e.g. vary the decimal values in a path in a manner minor enough to not effect the result, but still embed custom data). (Yes, any thief suspecting this could lower decimal precision or transform all values in a manner that might remove this.)
Trust in the law to protect his works, or provide a recourse if they are stolen.
Trust in the goodness of most of mankind to not do this.
Decide that theft is the sincerest form of flattery, and not worry about it. :)
I'm starting to venture out from using jpeg and gif files to png, I was wondering if there were any standards for using png beside IE's lack of support for it. I also want to know if there was any current articles about setting I should be using when optimizing for web? Right now I'm using photoshop to do this, should I be using firework instead?
Which optimizations you use depends on the type of image. If your image contains only few colors, you might use png-8, otherwise you may need png-24. Same goes for the use of transparency/alpha blending.
The Photoshop save for web-feature does a fine job, but when your website has a lot of visitors, you may benefit from using PNGCrush for further compressing your images. You can use the YSlow plugin for FireFox to test how much bandwidth you can save by crushing your images.
Also, you can make use of CSS-sprites if your design allows it. This can result in less (but larger) images and therefore less requests and sometimes less bandwidth. But this doen't depend on the type of images you use.
Png is supported by IE, by the way. Only the alpha-transparency is not supported by IE 6, but there are CSS/Javascript trics to work around that, although they do not work for background images.
I wouldn't quit using jpg. Jpg is very useful when it comes to pictures. Png files are convenient for small images like buttons, graphical elements, and for images with large plain areas, like screenshots.
Let me describe the "battlefield" of my task:
Multi-room audio/video chat with more than 1M users;
Custom Direct3D renderer;
What I need to implement is a TextOverVideo feature. The Text itself goes via network and is to be rendered on the recipient side with Direct3D renderer. AFAIK, it is commonly used in game development to create your own texture with letters/numbers and draw this items. Because our application must support many languages, we ought to use a standard. That's why I've been working with ID3DXFont interface but I've found out some unsatisfied limitations.
What I've faced is a lack of scalability. E.g. if user is resizing video window I have to RE-create D3DXFont with new D3DXFONT_DESC while he's doing that. I think it is unacceptable.
That is why the ONLY solution I see (due to my skills) is somehow render the text to a texture and therefore draw sprite with scaling, translation etc.
So, I'm not sure if I go into the correct direction. Please help with advice, experience, literature, sources...
Your question is a bit unclear. As I understand it, you want easily scalable font.
I think it is unacceptable
As far as I know, this is standard behavior for fonts - even for system fonts. They aren't supposed to be easily scalable.
Possible solutions:
Use ID3DXRenderTarget for rendering text onto texture. Font will be filtered when you scale it up too much. Some people will think that it looks ugly.
Write custom library that supports vector fonts. I.e. - it should be able to extract font outline from font, and build text from it. It will be MUCH slower than ID3DXFont (which is already slower than traditional "texture" fonts). Text will be easily scalable. Using this way, you are very likely to get visible artifacts ("noise") for small text. I wouldn't use that approach unless you want huge letters (40+ pixels). Freetype library may have functions for processing font outlines.
Or you could try using D3DXCreateText. This will create 3D text for ONE string. Won't be fast at all.
I'd forget about it. As long as user is happy about overall performance, improving font rendering routines (so their behavior looks nice to you) is not worth the effort.
--EDIT--
About ID3DXRenderTarget.
EVen if you use ID3DXRenderTarget, you'll need ID3DXFont. I.e. you use ID3DXFont to render text onto texture, and then use texture to blit text onto screen.
Because you said that performance is critical, you can delay creation of new ID3DXFont until user stops resizing video. I.e. When user starts resizing video, you use old font, but upscale it using texture. There will be filtering, of course. Once user stops resizing, you create new font when you have time. you probably can do that in separate thread, but I'm not sure about it. OR you could simply always render text in the same resolution as video. This way you won't have to worry about resizing it (it still will be filtered - along with the video). Some video players work this way.
Few more things about ID3DXFont. There is one problem with ID3DXFont - it is slow in situations where you need a lot of text (but you still need it, because it supports unicode, and writing texturefont with unicode support is pain). Last time I worked with it I optimized things by caching commonly used strings in the textures. I.e. any string that was drawn more than 3 frames in the row were rendered onto D3DFMT_A8R8G8B8 texture/render target, and then I've been copying that string from texture instead of using ID3DXFont. Strings that weren't rendered for a while, were removed from texture. That gave some serious boost. This solution, however is tricky - monitoring empty space in the texture, removing unused strings, and defragmenting the texture isn't exactly trivial (there is nothing exceptionally complicated, but it is easy to make a mistake). You won't need such complicated system unless your screen is literally covered by text.
ID3DXFont fonts are flat, always parallel to the screen. D3DXCreateText are meshes that can be scaled and rotated.
Texture fonts are fuzzy and don't look very clear. Not good for an app that uses lots of small text.
I am writing an app that can create 500 text meshes, each mesh averaging 3,000-5,000 vertices. The text meshes are created once, then are static. I get 700 fps on a GeForce 8800.