I am standing between major decision in my WP7 application. It's majore purpose is to display images, always one at a time on fullscreen.
I need perfect support for pinch to zoom, moving image (while zoomed) and switching between images via flick gesture. Most of these things are already implemented in WebBrowser control, so I would just have to generate proper html source with path to image in Isolated storage.
Or should I use common Image control and implement these gestures on my own? I would like your advice before I make this decision.
Are you targeting Windows Phone 8 or 7?
Generally, I would implement my own.
Issues with using the web-browser:
1. Perf is going to be slower.
Memory footprint is going to be higher (though I doubt you really care about this - it's not going to be massive).
If you are going to favorite/download images, it will be harder (if at all possible) to navigate to them in the browser.
The background will always be white, unless you generate HTML each time that will control that bit.
The biggest issue is that the zooming in/out will be.. Janky... You won't be able to control how zoomed out the user can make it - meaning that they can zoom out enough to make the picture very small and it won't "snap back".
It's not a bad stop-gap, and the issues with it are not so big that one can say "no - don't do it", but they are enough that you should reconsider.
Related
I'm working on a tinny software (C# and WPF) that does some filtering to the screen output. Examples on the filtering I'm talking about:
Customizable blue light filtering.
Increase/Decrease screen brightness (via changing the colors, not actual brightness)
Inverting screen colors.
And some more, but the simple idea is to tweak the pixel values of the screen after everything else is done rendering, but before showing the result.
Q1: How can I actually access (and then edit) the screen image/frame?
I've heard of getting and editing the screen DC directly (Win32) but I don't know if it's a good way, nor how to do it exactly.
Q2: what is the best way of applying these filters?
I think that tweaking every single pixel individually is a really bad way of doing it. (My code runs on the CPU and this process needs to be done every frame!)
Q3: Is there an event or hook for when windows is refreshing/updating the screen?
If yes, how can I register this process to it?
Note: I want a really performant way so that I don't lose any frame rate if possible.
Note: My preferred language for this is C#, C++ is ok.
Thanks a ton.
I have a C# application that has an existing WinForm that I now need to display upside down.
The application will be displayed on a touchscreen Windows 7 device. If two people are using the device, one person is viewing it right-side-up while another user will be simultaneously viewing it upside-down. I will need to have one control displayed right-side-up while another control is displayed upside-down, each duplicate forms. Both need to be functional. It is not necessary for the title bar and Windows close, maximize, and minimize to be rotated.
Is there a way to easily rotate this Form and all of its contents without having to rewrite it from scratch?
Unfortunately, rotating controls is not directly possible in WinForms.
At least, not if you want them to retain their functionality. It would be relatively simple to draw the control into a bitmap, rotate the bitmap, and then draw that back to the desired location on the form. But you would obviously lose the ability to interact with the controls. They would just be static representatives of their original selves.
But making functional upside-down controls just isn't going to happen. I mean, you could try to write a bunch of custom drawing code for owner-drawn controls, but you'll still run into a bunch of bugs, corner cases, and compatibility problems. The Win32 controls that WinForms is based on just don't support this. No big surprise, really, considering they were invented some 20–25 years before anyone thought of computer screens that you could carry around in your pocket and rotate in any direction. There is a good reason that UI technologies like WPF came out around the time that touch screens and tablets did.
There are some possibilities that can be explored when it comes to flipping the entire screen, but that's not going to help when you want different controls going different directions. (And I guess it betrays my vantage point as a desktop app guy when I say this, but that just sounds like an incredibly confusing UI.)
If you absolutely have to have this, someone else is going to have to give you another route to hack it, perhaps along the lines of Dhawalk's comment: hosting the WinForms control inside of a WPF app that does provide built-in support for rotated controls. I don't know enough about this to make any concrete suggestions down that path. From a few minutes of searching, it appears that WindowsFormsHost does not actually support rotation transforms, so this may be a non-starter anyway.
I'm currently working on an application with the need to display large engineering drawings that can be 8800x6800 or larger. The requirements state that the user should be able to pan and zoom the image. Ideally, they'd like to be able to annotate the images as well. If you look at the Windows Photo Viewer, you'll see the performance and features I'm looking to emulate, minus the annotation part.
So far, I've tried a couple different approaches for displaying the images and none seem to offer the performance that I'm looking for. Either they take up a lot of memory or they're slow. These are the approaches I've taken:
Viewbox with the Image as a child. Memory usage is OK, but re-sizing the Viewbox is slow. I haven't tried zooming/panning with this approach yet because of that.
InkCanvas with the Image set either as the background or as a child. With this approach zooming/panning by way of ScaleTransform and TranslateTransform seemed so-so, but memory usage could be up in the 450-600 MB range.
This is my first foray into image manipulation with .NET/WPF and my knowledge on the subject is fairly limited. What are some best-practices for dealing with large images, especially with WPF? I've read that tiling the image (like deep zoom) can help, but was unsure on how to do this or if it's the best idea in my situation. Do you know of any resources that might help me understand this better?
By "tiling" if you mean splitting the image up into separate pieces and only displaying a small subset at once to improve performance, this would be called "virtualisation".
Microsoft has an excellent blog about virtualising items and even provides a reference implementation of a VirtualCanvas which you can use as the starting point for a virtualised control.
Link here: https://learn.microsoft.com/en-us/archive/blogs/jgoldb/virtualized-wpf-canvas
Note that this blog includes zoom and scale as part of the discussion as well as a discussion about smooth scrolling and pre-emptive loading of tiles for best UI responsiveness.
I've been writing a small desktop gadget-type application that displays scrolling text along the bottom of the screen (Similar to the old CNN news ticker), however the performance of GDI is just unsatisfactory (As high as 8-12% on a quad core and 20% on a single core) even after I've attempted to clean out bottlenecks.
I was considering using OpenGL instead to render everything, but I don't know if that is a reasonable option to require users to have hardware acceleration for a tiny app like this.
Does anybody have any input on this?
If you're comfortable with using OpenGL and your intended users are happy with the additional dependencies that OpenGL brings then I say go for it. :)
In terms of staying with GDI, I'd make sure you're rendering the text a few times as possible (through such techniques as rendering to bitmap and just scrolling that instead).
If neither one of those two options sounds appealing then there's always DirectX.
You could write the app in WPF and let WPF handle the acceleration for you (it's backed by DirectX).
I wouldn't want to install open gl for a program like that. You say that you "attempted" to eliminate the bottlenecks, but it does not sound like you succeeded. Like lzcd mentioned, there are other ways to scroll text than to repaint it constantly. Why not just draw to a bitmap and scroll that?
How is scrolling typically handled in a Windows application that has computationally expensive graphics to render? For example, if I am rendering a waveform graph of a sound, after processing the wave form from a peakfile, should I:
Render the entire graphical representation to an in-memory GDI surface, and then simply have a scrollable control change the start/end of the render area?
Render the visible portion of the wave only. In a separate thread, process any new chunks of the graphc that come into view.
Render the visible portion of the wave, plus a buffer. This way, there's less of a chance of the user seeing "blank" or "currently rendering" portions of the waveform. Still, if a user quickly scrolls to a distant area, the whole section will be blank until rendering is complete.
The problem is, many applications handle this in different ways.
For example:
Adobe Acrobat - renders blank pages during scroll unless page is in cache. Any pages that would be visible within the document render area are rendered in a separate thread and are presented opon completion.
Microsoft Word - Essentially, the same as above. Documents are separated into distinct pages, so each page is processed/rendered on an as-needed basis and added to a cache.
Internet Explorer - Unknown. It appears that an entire "webpage" is rendered in graphic memory, no matter how many "screens" worth of graphic data it consumes. Theoretically, with a web page that scrolls for 10 or 15 screen lengths, this could mean 50-60MB worth of graphic memory consumption. Could anyone with experience with WebKit or FireFox explain whether or not the rendering engine favors consuming a ton of memory, or tries to render peices of the page "on the fly" to conserve memory?
If it helps, my application is based on C#, .NET 3.5, and WinForms.
This is a complexity vs. user experience trade-off. Your third option will give you the best user experience (they can start to see things right away and start to work). It is also the most complex to code (will take the longest to develop, with the most amount of bugs to kill).
The "correct" solution depends on how "expensive" expensive is, and on the demands of your user base. I would select the option with the least complexity that will provide a user experience that will satisfy the bulk of the customers:
Make it as complex as it needs to be, but no more complex than that.
I think this is actually a memory-usage versus a processor-usage tradeoff. Your first option (rendering the entire wave on an appropriately-sized canvas, and then moving that canvas around with only a visible window portion showing) might be the best approach, assuming you have enough memory for it. After an initial rendering delay, the user experience will be smooth and seamless.
If you don't have enough memory for this, then you have to render the visible portion on the fly. I've written this application (WAV data viewer) many times, and usually GDI+ is more than fast enough to render portions (even large portions) of WAV data in realtime (with a high framerate above 30 fps, which produces perfectly smooth animation). The key to this, however, is not to render each sample value as a separate point - this would be dog slow. What you want to do is for each pixel on your X axis, scan the corresponding chunk of WAV samples to get the minimimum and maximum sample value, and then render a single line between these values.