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  • Pixel Perfect Collision Detection in HTML5 Canvas

    - by Armin Ronacher
    Hi, I want to check a collision between two Sprites in HTML5 canvas. So for the sake of the discussion, let's assume that both sprites are IMG objects and a collision means that the alpha channel is not 0. Now both of these sprites can have a rotation around the object's center but no other transformation in case this makes this any easier. Now the obvious solution I came up with would be this: calculate the transformation matrix for both figure out a rough estimation of the area where the code should test (like offset of both + calculated extra space for the rotation) for all the pixels in the intersecting rectangle, transform the coordinate and test the image at the calculated position (rounded to nearest neighbor) for the alpha channel. Then abort on first hit. The problem I see with that is that a) there are no matrix classes in JavaScript which means I have to do that in JavaScript which could be quite slow, I have to test for collisions every frame which makes this pretty expensive. Furthermore I have to replicate something I already have to do on drawing (or what canvas does for me, setting up the matrices). I wonder if I'm missing anything here and if there is an easier solution for collision detection.

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  • "Beveled" Shapes in Quartz 2D

    - by Shaggy Frog
    I'm familiar with some of the basics of Quartz 2D drawing, like drawing basic shapes and gradients and so on, but I'm not sure how to draw a shape with a "beveled" look, like this: Essentially we've got a shine on one corner, and maybe some shading in the opposite corner. I think -- I didn't make this image, although I'd like to be able to approximate it. Any ideas? This is on the iPhone, and I'd like to use built-in frameworks and avoid any external libraries if at all possible.

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  • CGBitmapContextCreate: unsupported parameter combination

    - by tarmes
    I'm getting this error when creating a bitmap context: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 24 bits/pixel; 3-component color space; kCGImageAlphaNone; 7936 bytes/row. Here's the code (note that the context is based on the parameters of an existing CGImage: context = CGBitmapContextCreate(NULL, (int)pi.bufferSizeRequired.width, (int)pi.bufferSizeRequired.height, CGImageGetBitsPerComponent(imageRef), 0, CGImageGetColorSpace(imageRef), CGImageGetBitmapInfo(imageRef)); Width is 2626, height is 3981. I've leaving bytesPerRow at zero so that it gets calculated automatically for me, and it's chosen 7936 of its own accord. So, where on Earth is the inconsistency? It's driving me nuts.

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  • glTexImage2D behavior on iPhone and other OpenGL ES platforms

    - by spurserh
    Hello, I am doing some work which involves drawing video frames in real time in OpenGL ES. Right now I am using glTexImage2D to transfer the data, in the absence of Pixel Buffer Objects and the like. I suspect that the use of glTexImage2D with one or two frames of look-ahead, that is, using several textures so that the glTexImage2D call can be initiated a frame or two ahead, will allow for sufficient parallelism to play in real time if the system is capable of it at all. Is my assumption true that the driver will handle the actual data transfer to the hardware asynchronously after glTexImage2D returns, assuming I don't try to use the texture or call glFinish/glFlush? Is there a better way to do this with OpenGL ES? Thank you very much, Sean

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  • Design crowd sourcing

    - by CVertex
    I'm looking to get a logo designed, but all my designer friends/colleagues are pretty busy. Since I've never done it before, I thought it would be interesting to crowd source the design. Does anyone know of any good design crowd sourcing sites?

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  • Emulating old-school sprite flickering (theory and concept)

    - by Jeffrey Kern
    I'm trying to develop an oldschool NES-style video game, with sprite flickering and graphical slowdown. I've been thinking of what type of logic I should use to enable such effects. I have to consider the following restrictions if I want to go old-school NES style: No more than 64 sprites on the screen at a time No more than 8 sprites per scanline, or for each line on the Y axis If there is too much action going on the screen, the system freezes the image for a frame to let the processor catch up with the action From what I've read up, if there were more than 64 sprites on the screen, the developer would only draw high-priority sprites while ignoring low-priority ones. They could also alternate, drawing each even numbered sprite on opposite frames from odd numbered ones. The scanline issue is interesting. From my testing, it is impossible to get good speed on the XBOX 360 XNA framework by drawing sprites pixel-by-pixel, like the NES did. This is why in old-school games, if there were too many sprites on a single line, some would appear if they were cut in half. For all purposes for this project, I'm making scanlines be 8 pixels tall, and grouping the sprites together per scanline by their Y positioning. So, dumbed down I need to come up with a solution that.... 64 sprites on screen at once 8 sprites per 'scanline' Can draw sprites based on priority Can alternate between sprites per frame Emulate slowdown Here is my current theory First and foremost, a fundamental idea I came up with is addressing sprite priority. Assuming values between 0-255 (0 being low), I can assign sprites priority levels, for instance: 0 to 63 being low 63 to 127 being medium 128 to 191 being high 192 to 255 being maximum Within my data files, I can assign each sprite to be a certain priority. When the parent object is created, the sprite would randomly get assigned a number between its designated range. I would then draw sprites in order from high to low, with the end goal of drawing every sprite. Now, when a sprite gets drawn in a frame, I would then randomly generate it a new priority value within its initial priority level. However, if a sprite doesn't get drawn in a frame, I could add 32 to its current priority. For example, if the system can only draw sprites down to a priority level of 135, a sprite with an initial priority of 45 could then be drawn after 3 frames of not being drawn (45+32+32+32=141) This would, in theory, allow sprites to alternate frames, allow priority levels, and limit sprites to 64 per screen. Now, the interesting question is how do I limit sprites to only 8 per scanline? I'm thinking that if I'm sorting the sprites high-priority to low-priority, iterate through the loop until I've hit 64 sprites drawn. However, I shouldn't just take the first 64 sprites in the list. Before drawing each sprite, I could check to see how many sprites were drawn in it's respective scanline via counter variables . For example: Y-values between 0 to 7 belong to Scanline 0, scanlineCount[0] = 0 Y-values between 8 to 15 belong to Scanline 1, scanlineCount[1] = 0 etc. I could reset the values per scanline for every frame drawn. While going down the sprite list, add 1 to the scanline's respective counter if a sprite gets drawn in that scanline. If it equals 8, don't draw that sprite and go to the sprite with the next lowest priority. SLOWDOWN The last thing I need to do is emulate slowdown. My initial idea was that if I'm drawing 64 sprites per frame and there's still more sprites that need to be drawn, I could pause the rendering by 16ms or so. However, in the NES games I've played, sometimes there's slowdown if there's not any sprite flickering going on whereas the game moves beautifully even if there is some sprite flickering. Perhaps give a value to each object that uses sprites on the screen (like the priority values above), and if the combined values of all objects w/ sprites surpass a threshold, introduce the sprite flickering? IN CONCLUSION... Does everything I wrote actually sound legitimate and could work, or is it a pipe dream? What improvements can you all possibly think with this game programming theory of mine?

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  • How to set a Transparent Background of JPanel

    - by Imran
    Hi, I need to know if a JPanel`s bacground can be set to Transparent? My frame is has two Jpanels Image Panel and Feature Panel, Feature Panel is overlapping Image Panel, the Image Panel is working as a background and it is loading image from a remote Url, now I want to draw shaps on Feature Panel , but now Image Panel cannot be seen due to Feature Panel's background color. I need to make Feature Panel background transparent while still drawing its shapes and i want Image Panel to be visible since it is doing tiling and cache function of images. I need to seperate the image drawing and shape drawing thats why I`m using two jPanels! is there anyway the overlapping Jpanel have a transparent background? thanks

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  • Allow horizontal scrolling only in the core-plot barchart?

    - by Madhup
    Hi all, I am using core-plot lib to draw bar charts in my app like this My problem is that i want the enabling of grapgh movement only in horizontal direction so that I can see the records for a long period of time, But the problem is that i just wnt to keep the y axis fixed to its place, How can i do this? Waiting for help....

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  • What way to use the CGContext to draw is suitable?

    - by Tattat
    I know that the CGContext cannot call it to draw directly, and it needs to fill the drawing logic in the drawInContext, and call the CGContext to draw using "setNeedsDisplay", so, I designed a cmd to execute, but it cause some problems... like this : http://stackoverflow.com/questions/2617827/why-i-cant-draw-in-a-loop-using-uiview-in-iphone I think the CGContext is very different from my previous programming experience....(I used HTML5 canvas, that allow me add more details, after I draw, so do the Java Swing) Actually, I want to know what is the suitable to implement these kind of thing in Apples' programmer mind. Thz.

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  • Simple way to implement computer-go board in Java

    - by codingbear
    I want to make a simple Go board to design an Computer Go game. In a go game, you lie a "stone" (white or black) on a position where horizontal and vertical lines intersect. What are some simple ways to restrict users from placing their stones in other locations? Maybe I'm just not seeing a simple solution. EDIT I guess I should rephrase my question better: I want to know how to do the background image of Go board, so that I can lie my stones on the intersection of the horizontal and the vertical lines. I was thinking about getting a just regular Go board image, and when I'm actually rendering stones, I find right position of pixels to lie stones. However, that solution did not seem to be the best solution, since I need to worry about size of stone images and think about proportionality when I either expand or shrink the board window.

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  • Finding the centeroid of a polygon?

    - by user146780
    I have tried: for each vertex, add to total, divide by number of verities to get center. I'v also tried: Find the topmost, bottommost - get midpoint... find leftmost, rightmost, find midpoint. Both of these did not return the perfect center because I'm relying on the center to scale a polygon. I want to scale my polygons so I may put a border around them. What is the best way to find the centroid of a polygon given that the polygon may be concave, convex and have many many sides of various lengths. Thanks

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  • How does an unsharp mask work?

    - by Bob Aman
    I've been playing around with image processing lately, and I'd like to know how the unsharp mask algorithm works. I'm looking at the source code for Gimp and it's implementation, but so far I'm still in the dark about how it actually works. I need to implement it for a project I'm working on, but I'd like to actually understand the algorithm I'm using.

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  • Graph paper like drawing software

    - by Algorist
    Hi, I have a college assignment, where I have to draw diagrams of voronoi, delaunay, minimum spanning tree etc for the college. I want to do that in computer. I searched in google with no luck. Is there any good graph drawing software you are aware of? Thank you Bala

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  • Any 'pretty' data visualization libraries for Python?

    - by int3
    There are plenty of 'pretty-printing' visualization libraries for Javascript. E.g. those listed here. Googling for 'python visualization libraries' only turns up stuff like VTK and mayavi, which are primarily more for no-nonsense scientific use. So, do you know of any Python libraries similar to those Javascript ones in the above link? I particularly like the Javascript Infovis Toolkit.

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  • Turning an NSImage* into a CGImageRef?

    - by Brian Postow
    Is there an easy way to do this that works in 10.5? In 10.6 I can use nsImage CGImageForProposedRect: NULL context: NULL hints: NULL If I'm not using 1b black and white images (Like Group 4 TIFF), I can use bitmaps, but cgbitmaps seem to not like that setup... Is there a general way of doing this? I need to do this because I have an IKImageView that seems to only want to add CGImages, but all I've got are NSImages. Currently, I'm using a private setImage:(NSImage*) method that I'd REALLY REALLY rather not be using...

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  • How to view output .mp files from Functional MetaPost

    - by Jared Updike
    I'm interested in using Functional MetaPost on Mac OS X: http://cryp.to/funcmp/ I'm looking for a tutorial like: http://haskell.org/haskellwiki/Haskell_in_5_steps but for a trivial FuncMP example, i.e. using GHC, I can compile something simple such as: import FMP myPicture = text "blah" main = generate "foo" 1 myPicture but I can't figure out how to view this foo.1.mp output. (It gives a runtime error about not finding 'virmp'; my MetaPost binary is 'mpost'; I can't figure out how to override this Parameter or what my .FunMP file is or should be doing...) I can run mpost on that but the output (foo.1.1) is what, PostScript? EPS? How do I use this? (I imagine I just need a simple LaTeX file with an EPS figure in it or something...) Preferably, I'd like to generate output (.ps or .pdf that I can view) so I an actually get somewhere with Functional MetaPost, learning it, playing with it, not banging my head against paths and binaries and shell commands.

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  • How to keep text inside a circle using Cairo?

    - by miguelrios
    I a drawing a graph using Cairo (pycairo specifically) and I need to know how can I draw text inside a circle without overlapping it, by keeping it inside the bounds of the circle. I have this simple code snippet that draws a letter "a" inside the circle: ''' Created on May 8, 2010 @author: mrios ''' import cairo, math WIDTH, HEIGHT = 1000, 1000 #surface = cairo.PDFSurface ("/Users/mrios/Desktop/exampleplaces.pdf", WIDTH, HEIGHT) surface = cairo.ImageSurface (cairo.FORMAT_ARGB32, WIDTH, HEIGHT) ctx = cairo.Context (surface) ctx.scale (WIDTH/1.0, HEIGHT/1.0) # Normalizing the canvas ctx.rectangle(0, 0, 1, 1) # Rectangle(x0, y0, x1, y1) ctx.set_source_rgb(255,255,255) ctx.fill() ctx.arc(0.5, 0.5, .4, 0, 2*math.pi) ctx.set_source_rgb(0,0,0) ctx.set_line_width(0.03) ctx.stroke() ctx.arc(0.5, 0.5, .4, 0, 2*math.pi) ctx.set_source_rgb(0,0,0) ctx.set_line_width(0.01) ctx.set_source_rgb(255,0,255) ctx.fill() ctx.set_source_rgb(0,0,0) ctx.select_font_face("Georgia", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD) ctx.set_font_size(1.0) x_bearing, y_bearing, width, height = ctx.text_extents("a")[:4] print ctx.text_extents("a")[:4] ctx.move_to(0.5 - width / 2 - x_bearing, 0.5 - height / 2 - y_bearing) ctx.show_text("a") surface.write_to_png ("/Users/mrios/Desktop/node.png") # Output to PNG The problem is that my labels have variable amount of characters (with a limit of 20) and I need to set the size of the font dynamically. It must fit inside the circle, no matter the size of the circle nor the size of the label. Also, every label has one line of text, no spaces, no line breaks. Any suggestion?

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  • deleting HBITMAP causes an access violation at runtime.

    - by Oliver
    Hi, I have the following code to take a screenshot of a window, and get the colour of a specific pixel in it: void ProcessScreenshot(HWND hwnd){ HDC WinDC; HDC CopyDC; HBITMAP hBitmap; RECT rt; GetClientRect (hwnd, &rt); WinDC = GetDC (hwnd); CopyDC = CreateCompatibleDC (WinDC); //Create a bitmap compatible with the DC hBitmap = CreateCompatibleBitmap (WinDC, rt.right - rt.left, //width rt.bottom - rt.top);//height SelectObject (CopyDC, hBitmap); BitBlt (CopyDC, //destination 0,0, rt.right - rt.left, //width rt.bottom - rt.top, //height WinDC, //source 0, 0, SRCCOPY); COLORREF col = ::GetPixel(CopyDC,145,293); // Do some stuff with the pixel colour.... delete hBitmap; ReleaseDC(hwnd, WinDC); ReleaseDC(hwnd, CopyDC); } the line 'delete hBitmap;' causes a runtime error: an access violation. I guess I can't just delete it like that? Because bitmaps take up a lot of space, if I don't get rid of it I will end up with a huge memory leak. My question is: Does releasing the DC the HBITMAP is from deal with this, or does it stick around even after I have released the DC? If the later is the case, how do I correctly get rid of the HBITMAP?

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  • Drawing performance with CGImageCreateWithJPEGDataProvider?

    - by Rnegi
    I've actually curious about this for the iPhone. I am getting an MJPEG stream from a server and trying to render it natively on the iphone (without the use of safari class). Reasons for this is because the safari class while CAN render MJPEG natively, does not do so at the framerate I would like. So I tried drawing it natively, but I've come up with performance issues, namely a syncing issue between what I'm getting from the server and what I am able to draw onto the screen of the phone. (There should be a little lag, but the drift gets really bad, which is what I want to avoid). So I have a connection set up to my server and I do get the JPEGS. It's just data I insert into a NSMutableArray buffer CFMutableDataRef _t_data_ref = (CFMutableDataRef)[_buffer_array objectAtIndex:0]; //CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData (_cf_buffer_data); CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData(_t_data_ref); CGImageRef image = CGImageCreateWithJPEGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault); CGImageRef imgRef = image; CGContextDrawImage(context, CGRectMake(0, 17, 380, 285), imgRef); CGImageRelease(image); CGDataProviderRelease(imgDataProvider); please note this is the gist of my code, but it should summarize what I am trying to accomplish with regards to drawing. Also in order to get the framerate in sync, I had to detach a separate thread that sleeps X seconds and calls [self setNeedsDisplay]. NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; // Top-level pool while(1) { //[NSThread sleepForTimeInterval:TIMER_REFRESH_VALUE]; //sleep(unsigned int ); usleep(MICRO_REFRESH_VALUE); if ([_buffer_array count] > 10) { //NSLog(@"stuff %d", [_buffer_array count]); //[self setNeedsDisplay]; [self performSelectorOnMainThread:@selector(setNeedsDisplay) withObject:nil waitUntilDone:NO]; } } [pool release]; // Release the objects in the pool. My buffer of jpeg data actually fills up quite quick, but I can't seem to actually consume what i'm getting at the same rate, actually much slower. Are there any documents that can describe what kind of performance tuning I can do to make it go faster when rendering the JPEG to the screen? Or am I kind of stuck here? Thanks!

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  • Reinterpret a CGImageRef using PyObjC in Python

    - by Michael Rondinelli
    Hi, I'm doing something that's a little complicated to sum up in the title, so please bear with me. I'm writing a Python module that provides an interface to my C++ library, which provides some specialized image manipulation functionality. It would be most convenient to be able to access image buffers as CGImageRefs from Python, so they could be manipulated further using Quartz (using PyObjC, which works well). So I have a C++ function that provides a CGImageRef representation from my own image buffers, like this: CGImageRef CreateCGImageRefForImageBuffer(shared_ptr<ImageBuffer> buffer); I'm using Boost::Python to create my Python bridge. What is the easiest way for me to export this function so that I can use the CGImageRef from Python? Problems: The CGImageRef type can't be exported directly because it is a pointer to an undefined struct. So I could make a wrapper function that wraps it in a PyCObject or something to get it to send the pointer to Python. But then how do I "cast" this object to a CGImageRef from Python? Is there a better way to go about this?

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  • Python class variables not defined with called from outside module

    - by Jimmy
    I am having some issues with calling a function outside of a module. The scenario is I have a small class library that is using turtle to do some drawing, the function within the module calls the classes also within the module and draws things, etc. This all works fine and dandy when I call the function from within the same file, but if I have another file and call myLib.scene() I get variable undefined errors. Code examples: a class class Rectangle(object): def __init__(self, pen, height=100, width=100, fillcolor=''): self.pen = pen self.height = height self.width = width self.fillcolor = fillcolor def draw(self, x, y): '''draws the rectangle at coordinates x and y''' self.pen.goto(x, y) if self.fillcolor: self.pen.fillcolor(self.fillcolor) self.pen.fill(True) self.pen.down() for i in range(0,4): self.pen.forward(self.height if i%2 else self.width) self.pen.left(90) and the calling function is this def scene(pen): rect = Rectangle(pen) rect.draw(100,100) when I put the line scene(turtle.Turtle()) into the same file I have no issues, the rectangle is drawn and everyone goes home happy. However, if I try to call it from a separate python file like so: myLib.scene(turtle.Turtle()) I get an error: NameError: global name 'pen' is not defined, in the for loop of my draw method. Even if the line above is in the same file it still bombs out. What is going on?

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