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  • Scan-Line Z-Buffering Dilemma

    - by Belgin
    I have a set of vertices in 3D space, and for each I retain the following information: Its 3D coordinates (x, y, z). A list of pointers to some of the other vertices with which it's connected by edges. Right now, I'm doing perspective projection with the projecting plane being XY and the eye placed somewhere at (0, 0, d), with d < 0. By doing Z-Buffering, I need to find the depth of the point of a polygon (they're all planar) which corresponds to a certain pixel on the screen so I can hide the surfaces that are not visible. My questions are the following: How do I determine to which polygon does a pixel belong to so I could use the formula of the plane which contains the polygon to find the Z-coordinate? Are my data structures correct? Do I need to store something else entirely in order for this to work? I'm just projecting the vertices onto the projection plane and joining them with lines based on the pointer lists.

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  • Create Adventure Game Scene/Room/Backdrop from Real Photo

    - by Lyuben
    Is there a suitable software or a good tutorial for creating 2D rooms/scenery for adventure games from real photos? Is it possible to achieve good results by using photos, or the hand-drawn style will always be the best choice? Thank you! --- EDIT --- I want to clarify that I'm particularly interested in the art creation process, not on the environment in which to build games. I'm writing the game in Java for Android, but I don't think it matters. Also, I'm not trying to decide if the game will have photo realistic rooms or not - I want to achieve 2d pixelated, old-school style background scenes and I wonder if this can be made from photos, because I cannot draw them myself. For example, can I shoot a scene with my camera and then make it look something like the image in the following link: PIXEL ART FOREST I know that I cannot get the same quality as an absolutely hand-drawn pixel, but I'm looking for some decent technology/tutorial/software to make them somewhat similar.

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  • Are these non-standard applications of rendering practical in games?

    - by maul
    I've recently got into 3D and I came up with a few different "tricky" rendering techniques. Unfortunately I don't have the time to work on this myself, but I'd like to know if these are known methods and if they can be used in practice. Hybrid rendering Now I know that ray-tracing is still not fast enough for real-time rendering, at least on home computers. I also know that hybrid rendering (a combination of rasterization and ray-tracing) is a well known theory. However I had the following idea: one could separate a scene into "important" and "not important" objects. First you render the "not important" objects using traditional rasterization. In this pass you also render the "important" objects using a special shader that simply marks these parts on the image using a special color, or some stencil/depth buffer trickery. Then in the second pass you read back the results of the first pass and start ray tracing, but only from the pixels that were marked by the "important" object's shader. This would allow you to only ray-trace exactly what you need to. Could this be fast enough for real-time effects? Rendered physics I'm specifically talking about bullet physics - intersection of a very small object (point/bullet) that travels across a straight line with other, relatively slow-moving, fairly constant objects. More specifically: hit detection. My idea is that you could render the scene from the point of view of the gun (or the bullet). Every object in the scene would draw a different color. You only need to render a 1x1 pixel window - the center of the screen (again, from the gun's point of view). Then you simply check that central pixel and the color tells you what you hit. This is pixel-perfect hit detection based on the graphical representation of objects, which is not common in games. Afaik traditional OpenGL "picking" is a similar method. This could be extended in a few ways: For larger (non-bullet) objects you render a larger portion of the screen. If you put a special-colored plane in the middle of the scene (exactly where the bullet will be after the current frame) you get a method that works as the traditional slow-moving iterative physics test as well. You could simulate objects that the bullet can pass through (with decreased velocity) using alpha blending or some similar trick. So are these techniques in use anywhere, and/or are they practical at all?

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  • Things to do to port game made for iOS in Unity to Android?

    - by 2600th
    I have just made my first game for iOS and submitted it to app store. I was thinking of porting my game to Android also. I would like to know things one need to do/remember to port game made for iOS in Unity to Android. How to handle different screen resolutions and pixel densities, optimizations required, etc. Any other suggestions and important things you think I should know? EDIT: Also, should I handle builds according to device resolutions or by pixel density?

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  • Without using a pre-built physics engine, how can I implement 3-D collision detection from scratch?

    - by Andy Harglesis
    I want to tackle some basic 3-D collision detection and was wondering how engines handle this and give you a pretty interface and make it so easy ... I want to do it all myself, however. 2-D collision detection is extremely simple and can be done multiple ways that even beginner programmers could think up: 1.When the pixels touch; 2.when a rectangle range is exceeded; 3.when a pixel object is detected near another one in a pixel-based rendering engine. But 3-D is different with one dimension, but complex in many more so ... what are the general, basic understanding/examples on how 3-D collision detection can be implemented? Think two shaded, OpenGL cubes that are moved next to each other with a simple OpenGL rendering context and keyboard events.

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  • Java graphic objects as in flashgames

    - by Ryu Kajiya
    How is it possible (with the standard Java2D engine) to use small sprites like graphic objects? For those who don't know what I mean, in all those Flash-games like on Facebook they put small sprites on the screen which react to mouse-over and clicks. I tried to do the same in Java but can't find a good method. Swing components always spread over the whole bitmap, but I only want to get a reaction from the object when the mouse is over a pixel that's not transparent. So basically checking every time if the object below the mouse contains a non-transparent pixel (which i believe could be pretty intense in a gameloop or repaint loop). I have no idea how to implement such a thing efficiently.

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  • openGL textures in bitmap mode

    - by evenex_code
    For reasons detailed here I need to texture a quad using a bitmap (as in, 1 bit per pixel, not an 8-bit pixmap). Right now I have a bitmap stored in an on-device buffer, and am mounting it like so: glBindBuffer(GL_PIXEL_UNPACK_BUFFER, BFR.G[(T+1)%2]); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, W, H, 0, GL_COLOR_INDEX, GL_BITMAP, 0); The OpenGL spec has this to say about glTexImage2D: "If type is GL_BITMAP, the data is considered as a string of unsigned bytes (and format must be GL_COLOR_INDEX). Each data byte is treated as eight 1-bit elements..." Judging by the spec, each bit in my buffer should correspond to a single pixel. However, the following experiments show that, for whatever reason, it doesn't work as advertised: 1) When I build my texture, I write to the buffer in 32-bit chunks. From the wording of the spec, it is reasonable to assume that writing 0x00000001 for each value would result in a texture with 1-px-wide vertical bars with 31-wide spaces between them. However, it appears blank. 2) Next, I write with 0x000000FF. By my apparently flawed understanding of the bitmap mode, I would expect that this should produce 8-wide bars with 24-wide spaces between them. Instead, it produces a white 1-px-wide bar. 3) 0x55555555 = 1010101010101010101010101010101, therefore writing this value ought to create 1-wide vertical stripes with 1 pixel spacing. However, it creates a solid gray color. 4) Using my original 8-bit pixmap in GL_BITMAP mode produces the correct animation. I have reached the conclusion that, even in GL_BITMAP mode, the texturer is still interpreting 8-bits as 1 element, despite what the spec seems to suggest. The fact that I can generate a gray color (while I was expecting that I was working in two-tone), as well as the fact that my original 8-bit pixmap generates the correct picture, support this conclusion. Questions: 1) Am I missing some kind of prerequisite call (perhaps for setting a stride length or pack alignment or something) that will signal to the texturer to treat each byte as 8-elements, as it suggests in the spec? 2) Or does it simply not work because modern hardware does not support it? (I have read that GL_BITMAP mode was deprecated in 3.3, I am however forcing a 3.0 context.) 3) Am I better off unpacking the bitmap into a pixmap using a shader? This is a far more roundabout solution than I was hoping for but I suppose there is no such thing as a free lunch.

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  • Ho to make Histogram Normalize and Equalize in java using JAI library?

    - by Jay
    I m making App in java using Swing component and JAI library. I make histogram of black and white or gray scale image.Is this method of making histogram correct? iif it is correct then how can i do normalization and Equalization of histogram in my App in java using JAI library?my code is below. in my code i make BufferedImage object and then make and plot histogram of that image . enter code here import java.awt.Color; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.IOException; import javax.media.jai.JAI; import javax.media.jai.PlanarImage; import javax.swing.*; public class FinalHistogram extends JPanel { static int[] bins = new int[256]; static int[] newBins = new int[256]; static int x1 = 0, y1 = 0; static PlanarImage image = JAI.create("fileload", "alp_finger.tiff"); static BufferedImage bi = image.getAsBufferedImage(); FinalHistogram(int[] pbins) { for (int i = 0; i < 256; i++) { bins[i] = pbins[i]; newBins[i] = 0; } repaint(); } @Override protected void paintComponent(Graphics g) { for (int i = 0; i < 256; i++) { g.drawLine(150 + i, 300, 150 + i, 300 - (bins[i] / 300)); if (i == 0 || i == 255) { String sr = new Integer((i)).toString(); g.drawString(sr, 150 + i, 305); } System.out.println("bin[" + i + "]===" + bins[i]); } } public static void main(String[] args) throws IOException { int[] sbins = new int[256]; int pixel = 0; int k = 0; for (int x = 0; x < bi.getWidth(); x++) { for (int y = 0; y < bi.getHeight(); y++) { pixel = bi.getRaster().getSample(x, y, 0); k = (int) (pixel / 256); sbins[k]++; //pixel = bi.getRGB(x, y) & 0x000000ff; //k=pixel; //int[] pixels = m_image.getRGB(0, 0, m_image.getWidth(), m_image.getHeight(), null, 0, m_image.getWidth()); //short currentValue = 0; //int red,green,blue; //for(int i = 0; i<pixels.length; i++){ //red = (pixels[i] >> 16) & 0x000000FF; //green = (pixels[i] >>8 ) & 0x000000FF; //blue = pixels[i] & 0x000000FF; //currentValue = (short)((red + green + blue) / 3); //Current value gives the average //Disregard the alpha //assert(currentValue >= 0 && currentValue <= 255); //Something is awfully wrong if this goes off... //m_histogramArray[currentValue] += 1; //Increment the specific value of the array //} } } JTabbedPane jtp = new JTabbedPane(); jtp.addTab("Histogram", new JScrollPane(new FinalHistogram(sbins))); JFrame frame = new JFrame(); frame.setSize(500, 500); frame.add(new JScrollPane(jtp)); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }

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  • What's the state of the art in image upscaling?

    - by monov
    I like to collect cool pics and use them as wallpapers or for other things. Often, artists publish only low-res versions, probably for fear of theft. Example: Gabriel Pulecio's BIRDS Now, if I want to use that as a wallpaper, I'd have to upscale it, and obviously that'd make it look blurry because of the bicubic interpolation. I realize there's no real way to get a high-res version from a low-res pic, because the information is not simply there. That said, I'm wondering if heuristics have been developed for upscaling with less apparent loss of quality. Those would probably be optimized for specific image types. For photorealistic pictures, for cartoons with large flat areas, for pixel art... One algorithm I'm aware of is Seam Carving. It works for some kinds of pics, especially ones with a plain, undetailed or uninteresting background, and a subject that strongly stands out. But it's far from being general-purpose. Applying it to the above pic produces this. It looks quite sharp, but the proportions are horribly distorted because the algorithm is not designed for this kind of pic. Another is Pixel art scaling algorithms. Those are completely unfit for anything other than actual pixel art that's pixelized to begin with. For example, I tried the scale2x windows binary on my pic, but its output was nearly indistinguishable from nearest-neighbour scaling because the algorithm didn't detect any isolated pixely fragments to work from. Something else I tried was: I enlarged the image in Photoshop with bicubic interpolation, then I applied unsharp mask. The result looks pretty bad. The red blotch is actually resized reasonably well, but the dove is far from it. What I'm looking for is some app that makes a best-effort attempt at upscaling any input image while minimizing blurriness. If you know of any, I'll be thankful. Note that the subjective prettiness and sharpness of the result is what matters... the result doesn't need to be completely faithful to the original small image.

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  • Bad font anti-aliasing in Ubuntu

    - by Juliano
    I'm switching from Fedora 8 to Ubuntu 9.04, and I can't seem to get it to get a good font anti-aliasing to work. It seems that Ubuntu's fontconfig tries to keep characters in integral pixel widths. This makes text more difficult to read, when 1 pixel is too thin and 2 pixels is too thick. Check the image below. In Fedora, when fontconfig anti-aliasing is enabled, fonts have their thickness proportional to the font size. Below, the thickness is different for 8, 9 and 10pt sizes. In Ubuntu, on the other hand, even when anti-aliasing is enabled, all 8, 9 and 10pt sizes have 1 pixel thickness. This makes reading larges amount of text difficult. I'm using the very same home directory, and I already checked that X resources are the same in both systems: ~% xrdb -query | grep Xft Xft.antialias: 1 Xft.dpi: 96 Xft.hinting: 1 Xft.hintstyle: hintfull Xft.rgba: none GNOME settings: ~% gconftool-2 -a /desktop/gnome/font_rendering antialiasing = grayscale hinting = full dpi = 96 rgba_order = rgb So, the question is: What should I change in the new box (Ubuntu) in order to get anti-aliasing like in the old box (Fedora)?

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  • Java: Send BufferedImage through Socket with a low bitdepth

    - by Martijn Courteaux
    Hi, The title says enough I think. I have a full quality BufferedImage and I want to send it through an OutputStream with a low bitdepth. I don't want an algorithm to change pixel by pixel the quality, so it is still a full-quality. So, the goal is to write the image (with the full resolution) through the OuputStream with a very small size. Thanks, Martijn

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  • Font Anti-Aliasing on iPad SDK

    - by Felix Khazin
    I'm using a custom pixel font on the iPad SDK, and I'm trying to find a way to disable font anti-aliasing for UIFont. Pixel fonts usually work best when they don't have Anti-aliasing. I disable it easily in Photoshop when I create static resources, but this time I need a dynamic output with the custom font. Any ideas? Thanks.

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  • How to make ARGB transparency using bitwise operators.

    - by Smejda
    I need to make transparency, having 2 pixels: pixel1: {A, R, G, B} - foreground pixel pixel2: {A, R, G, B} - background pixel A,R,G,B are Byte values each color is represented by byte value now I'm calculating transparency as: newR = pixel2_R * alpha / 255 + pixel1_R * (255 - alpha) / 255 newG = pixel2_G * alpha / 255 + pixel1_G * (255 - alpha) / 255 newB = pixel2_B * alpha / 255 + pixel1_B * (255 - alpha) / 255 but it is too slow I need to do it with bitwise operators (AND,OR,XOR, NEGATION, BIT MOVE)

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  • Centering a percent-based div

    - by Sarfraz
    Hello, Recently, a client asked that his site be percent-based rather than pixel-based. The percent was to be set to 80%. As you guys know, it is very easy to center the container if it is pixel-based but how do you center a percent-based main container? #container { width:80%; margin:0px auto; } That does not center the container :(

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  • AVFoundation buffer comparison to a saved image

    - by user577552
    Hi, I am a long time reader, first time poster on StackOverflow, and must say it has been a great source of knowledge for me. I am trying to get to know the AVFoundation framework. What I want to do is save what the camera sees and then detect when something changes. Here is the part where I save the image to a UIImage : if (shouldSetBackgroundImage) { CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); // Create a bitmap graphics context with the sample buffer data CGContextRef context = CGBitmapContextCreate(rowBase, bufferWidth, bufferHeight, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); // Create a Quartz image from the pixel data in the bitmap graphics context CGImageRef quartzImage = CGBitmapContextCreateImage(context); // Free up the context and color space CGContextRelease(context); CGColorSpaceRelease(colorSpace); // Create an image object from the Quartz image UIImage * image = [UIImage imageWithCGImage:quartzImage]; [self setBackgroundImage:image]; NSLog(@"reference image actually set"); // Release the Quartz image CGImageRelease(quartzImage); //Signal that the image has been saved shouldSetBackgroundImage = NO; } and here is the part where I check if there is any change in the image seen by the camera : else { CGImageRef cgImage = [backgroundImage CGImage]; CGDataProviderRef provider = CGImageGetDataProvider(cgImage); CFDataRef bitmapData = CGDataProviderCopyData(provider); char* data = CFDataGetBytePtr(bitmapData); if (data != NULL) { int64_t numDiffer = 0, pixelCount = 0; NSMutableArray * pointsMutable = [NSMutableArray array]; for( int row = 0; row < bufferHeight; row += 8 ) { for( int column = 0; column < bufferWidth; column += 8 ) { //we get one pixel from each source (buffer and saved image) unsigned char *pixel = rowBase + (row * bytesPerRow) + (column * BYTES_PER_PIXEL); unsigned char *referencePixel = data + (row * bytesPerRow) + (column * BYTES_PER_PIXEL); pixelCount++; if ( !match(pixel, referencePixel, matchThreshold) ) { numDiffer++; [pointsMutable addObject:[NSValue valueWithCGPoint:CGPointMake(SCREEN_WIDTH - (column/ (float) bufferHeight)* SCREEN_WIDTH - 4.0, (row/ (float) bufferWidth)* SCREEN_HEIGHT- 4.0)]]; } } } numberOfPixelsThatDiffer = numDiffer; points = [pointsMutable copy]; } For some reason, this doesn't work, meaning that the iPhone detects almost everything as being different from the saved image, even though I set a very low threshold for detection in the match function... Do you have any idea of what I am doing wrong?

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  • How to play YUV video in Qt4?

    - by shingle
    I want to play YUV video sequence by using Qt. Now I am using QPixmap, by using DrawPixel on QPixmap pixel by pixel. However, it can't play the video in real-time. How can I do to improve the speed?

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  • Use native HBitmap in C# while preserving alpha channel/transparency. Please check this code, it works on my computer...

    - by David
    Let's say I get a HBITMAP object/handle from a native Windows function. I can convert it to a managed bitmap using Bitmap.FromHbitmap(nativeHBitmap), but if the native image has transparency information (alpha channel), it is lost by this conversion. There are a few questions on Stack Overflow regarding this issue. Using information from the first answer of this question (How to draw ARGB bitmap using GDI+?), I wrote a piece of code that I've tried and it works. It basically gets the native HBitmap width, height and the pointer to the location of the pixel data using GetObject and the BITMAP structure, and then calls the managed Bitmap constructor: Bitmap managedBitmap = new Bitmap(bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); As I understand (please correct me if I'm wrong), this does not copy the actual pixel data from the native HBitmap to the managed bitmap, it simply points the managed bitmap to the pixel data from the native HBitmap. And I don't draw the bitmap here on another Graphics (DC) or on another bitmap, to avoid unnecessary memory copying, especially for large bitmaps. I can simply assign this bitmap to a PictureBox control or the the Form BackgroundImage property. And it works, the bitmap is displayed correctly, using transparency. When I no longer use the bitmap, I make sure the BackgroundImage property is no longer pointing to the bitmap, and I dispose both the managed bitmap and the native HBitmap. The Question: Can you tell me if this reasoning and code seems correct. I hope I will not get some unexpected behaviors or errors. And I hope I'm freeing all the memory and objects correctly. private void Example() { IntPtr nativeHBitmap = IntPtr.Zero; /* Get the native HBitmap object from a Windows function here */ // Create the BITMAP structure and get info from our nativeHBitmap NativeMethods.BITMAP bitmapStruct = new NativeMethods.BITMAP(); NativeMethods.GetObjectBitmap(nativeHBitmap, Marshal.SizeOf(bitmapStruct), ref bitmapStruct); // Create the managed bitmap using the pointer to the pixel data of the native HBitmap Bitmap managedBitmap = new Bitmap( bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); // Show the bitmap this.BackgroundImage = managedBitmap; /* Run the program, use the image */ MessageBox.Show("running..."); // When the image is no longer needed, dispose both the managed Bitmap object and the native HBitmap this.BackgroundImage = null; managedBitmap.Dispose(); NativeMethods.DeleteObject(nativeHBitmap); } internal static class NativeMethods { [StructLayout(LayoutKind.Sequential)] public struct BITMAP { public int bmType; public int bmWidth; public int bmHeight; public int bmWidthBytes; public ushort bmPlanes; public ushort bmBitsPixel; public IntPtr bmBits; } [DllImport("gdi32", CharSet = CharSet.Auto, EntryPoint = "GetObject")] public static extern int GetObjectBitmap(IntPtr hObject, int nCount, ref BITMAP lpObject); [DllImport("gdi32.dll")] internal static extern bool DeleteObject(IntPtr hObject); }

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  • How can I get image data from QTKit without color or gamma correction in Snow Leopard?

    - by Nick Haddad
    Since Snow Leopard, QTKit is now returning color corrected image data from functions like QTMovies frameImageAtTime:withAttributes:error:. Given an uncompressed AVI file, the same image data is displayed with larger pixel values in Snow Leopard vs. Leopard. Currently I'm using frameImageAtTime to get an NSImage, then ask for the tiffRepresentation of that image. After doing this, pixel values are slightly higher in Snow Leopard. For example, a file with the following pixel value in Leopard: [0 180 0] Now has a pixel value like: [0 192 0] Is there any way to ask a QTMovie for video frames that are not color corrected? Should I be asking for a CGImageRef, CIImage, or CVPixelBufferRef instead? Is there a way to disable color correction altogether prior to reading in the video files? I've attempted to work around this issue by drawing into a NSBitmapImageRep with the NSCalibratedColroSpace, but that only gets my part of the way there: // Create a movie NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys : nsFileName, QTMovieFileNameAttribute, [NSNumber numberWithBool:NO], QTMovieOpenAsyncOKAttribute, [NSNumber numberWithBool:NO], QTMovieLoopsAttribute, [NSNumber numberWithBool:NO], QTMovieLoopsBackAndForthAttribute, (id)nil]; _theMovie = [[QTMovie alloc] initWithAttributes:dict error:&error]; // .... NSMutableDictionary *imageAttributes = [NSMutableDictionary dictionary]; [imageAttributes setObject:QTMovieFrameImageTypeNSImage forKey:QTMovieFrameImageType]; [imageAttributes setObject:[NSArray arrayWithObject:@"NSBitmapImageRep"] forKey: QTMovieFrameImageRepresentationsType]; [imageAttributes setObject:[NSNumber numberWithBool:YES] forKey:QTMovieFrameImageHighQuality]; NSError* err = nil; NSImage* image = (NSImage*)[_theMovie frameImageAtTime:frameTime withAttributes:imageAttributes error:&err]; // copy NSImage into an NSBitmapImageRep (Objective-C) NSBitmapImageRep* bitmap = [[image representations] objectAtIndex:0]; // Draw into a colorspace we know about NSBitmapImageRep *bitmapWhoseFormatIKnow = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL pixelsWide:getWidth() pixelsHigh:getHeight() bitsPerSample:8 samplesPerPixel:4 hasAlpha:YES isPlanar:NO colorSpaceName:NSCalibratedRGBColorSpace bitmapFormat:0 bytesPerRow:(getWidth() * 4) bitsPerPixel:32]; [NSGraphicsContext saveGraphicsState]; [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithBitmapImageRep:bitmapWhoseFormatIKnow]]; [bitmap draw]; [NSGraphicsContext restoreGraphicsState]; This does convert back to a 'Non color corrected' colorspace, but the color values NOT are exactly the same as what is stored in the Uncompressed AVI files we are testing with. Also this is much less efficient because it is converting from RGB - "Device RGB" - RGB. Also, I am working in a 64-bit application, so dropping down to the Quicktime-C API is not an option. Thanks for your help.

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  • How do I prevent jagged edges alongside the surfaces of my 3d model?

    - by badcodenotreat
    Lets say I've implemented in openGL a crude model viewer with shading which renders a series of blocks, such that I have something that looks like this. http://i.imgur.com/TsF7K.jpg Whenever I rotate my model to the side, it causes an unwanted jagged effect along any surface with a steep viewing angle. http://i.imgur.com/Bgl9o.jpg I'm pretty sure this is due to the polygon offset I used to prevent z-fighting between the model and the wireframe, however I'm not able to find the factor/unit parameters in openGL which prevent this unwanted effect. what are the best values of factor and unit for glPolygonOffset to prevent this? would implementing anti-aliasing alleviate the problem? is the trade off in performance trivial/significant? is this perhaps a shading issue? should i try a solution along this line of thought?

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  • AS3 Transition Manager problem

    - by Mirko
    I am using the TransitionManager class to pixel dissolve an image in an image gallery XML driven. It always stops half way through the animation...I hate Adobe Tween engines, I always used TweenMax without (almost) any problem but I would like to have the pixel dissolve effect. var myTM:TransitionManager = new TransitionManager(container_mc); myTM.addEventListener("allTransitionsOutDone",swapContent); myTM.startTransition({ type:PixelDissolve, direction:Transition.OUT, duration:1,easing:None.easeOut,xSections:200, ySections:200 }); Any suggestion?

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  • Performance Optimization for Matrix Rotation

    - by Summer_More_More_Tea
    Hello everyone: I'm now trapped by a performance optimization lab in the book "Computer System from a Programmer's Perspective" described as following: In a N*N matrix M, where N is multiple of 32, the rotate operation can be represented as: Transpose: interchange elements M(i,j) and M(j,i) Exchange rows: Row i is exchanged with row N-1-i A example for matrix rotation(N is 3 instead of 32 for simplicity): ------- ------- |1|2|3| |3|6|9| ------- ------- |4|5|6| after rotate is |2|5|8| ------- ------- |7|8|9| |1|4|7| ------- ------- A naive implementation is: #define RIDX(i,j,n) ((i)*(n)+(j)) void naive_rotate(int dim, pixel *src, pixel *dst) { int i, j; for (i = 0; i < dim; i++) for (j = 0; j < dim; j++) dst[RIDX(dim-1-j, i, dim)] = src[RIDX(i, j, dim)]; } I come up with an idea by inner-loop-unroll. The result is: Code Version Speed Up original 1x unrolled by 2 1.33x unrolled by 4 1.33x unrolled by 8 1.55x unrolled by 16 1.67x unrolled by 32 1.61x I also get a code snippet from pastebin.com that seems can solve this problem: void rotate(int dim, pixel *src, pixel *dst) { int stride = 32; int count = dim >> 5; src += dim - 1; int a1 = count; do { int a2 = dim; do { int a3 = stride; do { *dst++ = *src; src += dim; } while(--a3); src -= dim * stride + 1; dst += dim - stride; } while(--a2); src += dim * (stride + 1); dst -= dim * dim - stride; } while(--a1); } After carefully read the code, I think main idea of this solution is treat 32 rows as a data zone, and perform the rotating operation respectively. Speed up of this version is 1.85x, overwhelming all the loop-unroll version. Here are the questions: In the inner-loop-unroll version, why does increment slow down if the unrolling factor increase, especially change the unrolling factor from 8 to 16, which does not effect the same when switch from 4 to 8? Does the result have some relationship with depth of the CPU pipeline? If the answer is yes, could the degrade of increment reflect pipeline length? What is the probable reason for the optimization of data-zone version? It seems that there is no too much essential difference from the original naive version. EDIT: My test environment is Intel Centrino Duo processor and the verion of gcc is 4.4 Any advice will be highly appreciated! Kind regards!

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  • How to tile a 30000 x 6000 image for a 480 x 320 screen?

    - by Horace Ho
    (this is related to another question about implementation on iPhone) I have a large image, size around 30000 (w) x 6000 (h) pixels. You may consider it's like a big map. I assume I need to crop it up into smaller tiles. Questions: what is the tile strategy? Requirements: whole image (though cropped) can be scrolled up/down/left/right by swipes zoom in (up to pixel-to-pixel) out (down to screen-fit-by-height) by the 2-finger operation memory efficiency by lazy loading tiles Thanks!

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  • Why do I get rows of zeros in my 2D fft?

    - by Nicholas Pringle
    I am trying to replicate the results from a paper. "Two-dimensional Fourier Transform (2D-FT) in space and time along sections of constant latitude (east-west) and longitude (north-south) were used to characterize the spectrum of the simulated flux variability south of 40degS." - Lenton et al(2006) The figures published show "the log of the variance of the 2D-FT". I have tried to create an array consisting of the seasonal cycle of similar data as well as the noise. I have defined the noise as the original array minus the signal array. Here is the code that I used to plot the 2D-FT of the signal array averaged in latitude: import numpy as np from numpy import ma from matplotlib import pyplot as plt from Scientific.IO.NetCDF import NetCDFFile ### input directory indir = '/home/nicholas/data/' ### get the flux data which is in ### [time(5day ave for 10 years),latitude,longitude] nc = NetCDFFile(indir + 'CFLX_2000_2009.nc','r') cflux_southern_ocean = nc.variables['Cflx'][:,10:50,:] cflux_southern_ocean = ma.masked_values(cflux_southern_ocean,1e+20) # mask land nc.close() cflux = cflux_southern_ocean*1e08 # change units of data from mmol/m^2/s ### create an array that consists of the seasonal signal fro each pixel year_stack = np.split(cflux, 10, axis=0) year_stack = np.array(year_stack) signal_array = np.tile(np.mean(year_stack, axis=0), (10, 1, 1)) signal_array = ma.masked_where(signal_array > 1e20, signal_array) # need to mask ### average the array over latitude(or longitude) signal_time_lon = ma.mean(signal_array, axis=1) ### do a 2D Fourier Transform of the time/space image ft = np.fft.fft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log(mgft) log_mgft= np.log(mgft) Every second row of the ft consists completely of zeros. Why is this? Would it be acceptable to add a randomly small number to the signal to avoid this. signal_time_lon = signal_time_lon + np.random.randint(0,9,size=(730, 182))*1e-05 EDIT: Adding images and clarify meaning The output of rfft2 still appears to be a complex array. Using fftshift shifts the edges of the image to the centre; I still have a power spectrum regardless. I expect that the reason that I get rows of zeros is that I have re-created the timeseries for each pixel. The ft[0, 0] pixel contains the mean of the signal. So the ft[1, 0] corresponds to a sinusoid with one cycle over the entire signal in the rows of the starting image. Here are is the starting image using following code: plt.pcolormesh(signal_time_lon); plt.colorbar(); plt.axis('tight') Here is result using following code: ft = np.fft.rfft2(signal_time_lon) mgft = np.abs(ft) ps = mgft**2 log_ps = np.log1p(mgft) plt.pcolormesh(log_ps); plt.colorbar(); plt.axis('tight') It may not be clear in the image but it is only every second row that contains completely zeros. Every tenth pixel (log_ps[10, 0]) is a high value. The other pixels (log_ps[2, 0], log_ps[4, 0] etc) have very low values.

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