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  • Optimizing drawing on UITableViewCell

    - by Brian
    I am drawing content to a UITableViewCell and it is working well, but I'm trying to understand if there is a better way of doing this. Each cell has the following components: Thumbnail on the left side - could come from server so it is loaded async Title String - variable length so each cell could be different height Timestamp String Gradient background - the gradient goes from the top of the cell to the bottom and is semi-transparent so that background colors shine through with a gloss It currently works well. The drawing occurs as follows: UITableViewController inits/reuses a cell, sets needed data, and calls [cell setNeedsDisplay] The cell has a CALayer for the thumbnail - thumbnailLayer In the cell's drawRect it draws the gradient background and the two strings The cell's drawRect it then calls setIcon - which gets the thumbnail and sets the image as the contents of the thumbnailLayer. If the image is not found locally, it sets a loading image as the contents of the thumbnailLayer and asynchronously gets the thumbnail. Once the thumbnail is received, it is reset by calling setIcon again & resets the thumbnailLayer.contents This all currently works, but using Instruments I see that the thumbnail is compositing with the gradient. I have tried the following to fix this: setting the cell's backgroundView to a view whose drawRect would draw the gradient so that the cell's drawRect could draw the thumbnail and using setNeedsDisplayInRect would allow me to only redraw the thumbnail after it loaded --- but this resulted in the backgroundView's drawing (gradient) covering the cell's drawing (text). I would just draw the thumbnail in the cell's drawRect, but when setNeedsDisplay is called, drawRect will just overlap another image and the loading image may show through. I would clear the rect, but then I would have to redraw the gradient. I would try to draw the gradient in a CAGradientLayer and store a reference to it, so I can quickly redraw it, but I figured I'd have to redraw the gradient if the cell's height changes. Any ideas? I'm sure I'm missing something so any help would be great.

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  • How do I arbitrarily distort a textured polygon?

    - by Archagon
    I'd like to write a program that lets me arbitrarily distort a textured polygon by dragging its vertices. I want the texture to distort fluidly and without overlap, assuming the new polygon doesn't intersect itself. I should also be able to repeat the process with the new shape, and with a minimum amount of loss. Are there any algorithms for doing this?

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  • imageWithCGImage and memory

    - by Adam Ernst
    If I use [UIImage imageWithCGImage:], passing in a CGImageRef, do I then release the CGImageRef or does UIImage take care of this itself when it is deallocated? The documentation isn't entirely clear. It says "This method does not cache the image object." Originally I called CGImageRelease on the CGImageRef after passing it to imageWithCGImage:, but that caused a malloc_error_break warning in the Simulator claiming a double-free was occurring.

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  • QPainter paints garbage

    - by DSblizzard
    Fragment of program code: def add_link(Item0Num, Item1Num): global Mw, View # Mw - MainWindow if Item0Num != Item1Num and not link_exists(Item0Num, Item1Num): append( links_to(Item1Num), Item0Num ) append( links_from(Item0Num), Item1Num ) LinkGi = TLinkGi() Mw.Scene.addItem(LinkGi) LinkGi.setZValue(200) LinkGi.scale(1 / View.Scale, 1 / View.Scale) LinkGi.Item0Num = Item0Num LinkGi.Item1Num = Item1Num class TLinkGi(QGraphicsItem): def paint(self, Painter, StyleOptionGraphicsItem, Widget): global Mw, View Pen = QPen(Qt.black, 1) Painter.setPen(Pen) X0, Y0 = task_center(self.Item0Num) self.setPos(X0, Y0) X1, Y1 = task_center(self.Item1Num) X, Y = int( (X1 - X0) * View.Scale ), int( (Y1 - Y0) * View.Scale ) Painter.drawLine(0, 0, X, Y) #Mw.Scene.update(0, 0, Plan.Size, Plan.Size) # (1) #Mw.gvMain.repaint() # (2) def boundingRect(self): global View Rect = QRectF(0, 0, Plan.Size, Plan.Size) return Rect This paints such garbage: http://img697.imageshack.us/content_round.php?page=done&l=img697/5395/qpaintergarbage1.jpg When lines (1) and (2) are uncommented things doesn't become much better: http://img63.imageshack.us/content_round.php?page=done&l=img63/9693/qpaintergarbage0.jpg Please help me to solve this problem.

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  • Video Synthesis - Making waves, pattern, gradients...

    - by Nathan
    I'm writing a program to generate some trippy visuals. My code paints each pixel with a random blue value which loops at 0.04 second intervals. for (y = 0; y < 5.5; y += 0.2) { for (x = 0; x < 7.5; x += 0.2) { b = rand() / ((double) RAND_MAX); setPixelColor(x,y,r,g,b); } } I'd like to do more than just make blue noise... but my maths is a bit rusty, and Google isn't helping me much today, so it would be great if you could share anything you know about making waves, patterns, gradient animations, etc or links to such material.

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  • tangent of two circles

    - by harryovers
    Hello, I am trying to write some code that that will draw the line which is a tangent between 2 circles. so far i have been able to draw multiple circles, and lines between the centers. i have a class which stores the values used in drawing the circles (radius, position). what i need is a method in this class to find all posible tangents between 2 circles. any help would be great. this is what i have so far (it could very well be a load of rubbish) public static Vector2[] Tangents(circle c1, circle c2) { if (c2.radius > c1.radius) { circle temp = c1; c1 = c2; c2 = temp; } circle c0 = new circle(c1.radius - c2.radius, c1.center); Vector2[] tans = new Vector2[2]; Vector2 dir = _point - _center; float len = (float)Math.Sqrt((dir.X * dir.X) + (dir.Y * dir.Y)); float angle = (float)Math.Atan2(dir.X, dir.Y); float tan_length = (float)Math.Sqrt((len * len) - (_radius * _radius)); float tan_angle = (float)Math.Asin(_radius / len); tans[0] = new Vector2((float)Math.Cos(angle + tan_angle), (float)Math.Sin(angle + tan_angle)); tans[1] = new Vector2((float)Math.Cos(angle - tan_angle), (float)Math.Sin(angle - tan_angle)); Vector2 dir0 = c0.center - tans[0]; Vector2 dir1 = c0.center - tans[1]; Vector2 tan00 = Vector2.Add(Vector2.Multiply(tans[0], (float)c2.radius), c1.center); Vector2 tan01 = c2.center; Vector2 tan10 = Vector2.Add(Vector2.Multiply(tans[1], (float)c2.radius), c1.center); Vector2 tan11 = c2.center; }

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  • Rendering to a single Bitmap object from multiple threads

    - by Lee Treveil
    What im doing is rendering a number of bitmaps to a single bitmap. There could be hundreds of images and the bitmap being rendered to could be over 1000x1000 pixels. Im hoping to speed up this process by using multiple threads but since the Bitmap object is not thread-safe it cant be rendered to directly concurrently. What im thinking is to split the large bitmap into sections per cpu, render them separately then join them back together at the end. I haven't done this yet incase you guys/girls have any better suggestions. Any ideas? Thanks

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  • How do I remove those rotation artefacts from my CATiledLayer?

    - by Felix
    Hello all, I have a CATiledLayer into which I render content in the following method - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx I used the QuartzDemo code to draw a pattern. This works very well until I apply a rotation transform to the layer's parentLayer (a UIView): rotated: These zigzag artefacts become worse when I start drawing lines and texts into the CATiledLayer. I applied the transform as follows (I also tried using an affine transform on the view itself): self.containerView.layer.transform = CATransform3DMakeRotation(angleRadians, 0.0f, 0.0f, 1.0f); I transform the containerView rather than the layer itself, as I have several layers in that view that I would like to rotate at the same time without changing the relative positions. I did not have problems when rotating UIImageViews in the past. Is there a way that I can rotate the CATiledLayer without these problems? Any help would be greatly appreciated. Yours, Felix

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  • Finding intersection of two spheres

    - by Onkar Deshpande
    Hi, Consider the following problem - I am given 2 links of length L0 and L1. P0 is the point that the first link starts at and P1 is the point that I want the end of second link to be at in 3-D space. I am supposed to write a function that should take in these 3-D points (P0 and P1) as inputs and should find all configurations of the links that put the second link's end point at P1. My understanding of how to go about it is - Each link L0 and L1 will create a sphere S0 and S1 around itself. I should find out the intersection of those two spheres (which will be a circle) and print all points that are on the circumference of that circle. I saw gmatt's first reply on the http://stackoverflow.com/questions/1406375/finding-intersection-points-between-3-spheres but could not understand it properly since the images did not show up. I also saw a formula for finding out the intersection at mathworld[dot]wolfram[dot]com/Sphere-SphereIntersection[dot]html . I could find the radius of intersection by the method given on mathworld. Also I can find the center of that circle and then use the parametric equation of circle to find the points. The only doubt that I have is will this method work for the points P0 and P1 mentioned above ? Please comment and let me know your thoughts.

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  • How to use Mesa3D on Mac OS X and Windows

    - by gutsblow
    Hello all, I need to use Mesa3D for a cross platform application(windows and Mac only) which uses only offline software rendering. The reason I wanted to use Mesa3D is because it has the same Drawing calls as OpenGL and they are really easy. Now I know that Apple itself has a software implementation (which I heard is flaky), but I prefer using Mesa so that it's a lot easier for me to maintain the code on both platforms. On windows I managed to compile three DLL's from the Mesa3d source, but don't know what to do with them. On Mac OS X I am completely clueless. I would highly appreciate your help. Thank you once again very much!

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  • CSG operations on implicit surfaces with marching cubes

    - by Mads Elvheim
    I render isosurfaces with marching cubes, (or perhaps marching squares as this is 2D) and I want to do set operations like set difference, intersection and union. I thought this was easy to implement, by simply choosing between two vertex scalars from two different implicit surfaces, but it is not. For my initial testing, I tried with two spheres, and the set operation difference. i.e A - B. One sphere is moving and the other one is stationary. Here's the approach I tried when picking vertex scalars and when classifying corner vertices as inside or outside. The code is written in C++. OpenGL is used for rendering, but that's not important. Normal rendering without any CSG operations does give the expected result. void march(const vec2& cmin, //min x and y for the grid cell const vec2& cmax, //max x and y for the grid cell std::vector<vec2>& tri, float iso, float (*cmp1)(const vec2&), //distance from stationary sphere float (*cmp2)(const vec2&) //distance from moving sphere ) { unsigned int squareindex = 0; float scalar[4]; vec2 verts[8]; /* initial setup of the grid cell */ verts[0] = vec2(cmax.x, cmax.y); verts[2] = vec2(cmin.x, cmax.y); verts[4] = vec2(cmin.x, cmin.y); verts[6] = vec2(cmax.x, cmin.y); float s1,s2; /********************************** ********For-loop of interest****** *******Set difference between **** *******two implicit surfaces****** **********************************/ for(int i=0,j=0; i<4; ++i, j+=2){ s1 = cmp1(verts[j]); s2 = cmp2(verts[j]); if((s1 < iso)){ //if inside sphere1 if((s2 < iso)){ //if inside sphere2 scalar[i] = s2; //then set the scalar to the moving sphere } else { scalar[i] = s1; //only inside sphere1 squareindex |= (1<<i); //mark as inside } } else { scalar[i] = s1; //inside neither sphere } } if(squareindex == 0) return; /* Usual interpolation between edge points to compute the new intersection points */ verts[1] = mix(iso, verts[0], verts[2], scalar[0], scalar[1]); verts[3] = mix(iso, verts[2], verts[4], scalar[1], scalar[2]); verts[5] = mix(iso, verts[4], verts[6], scalar[2], scalar[3]); verts[7] = mix(iso, verts[6], verts[0], scalar[3], scalar[0]); for(int i=0; i<10; ++i){ //10 = maxmimum 3 triangles, + one end token int index = triTable[squareindex][i]; //look up our indices for triangulation if(index == -1) break; tri.push_back(verts[index]); } } This gives me weird jaggies: It looks like the CSG operation is done without interpolation. It just "discards" the whole triangle. Do I need to interpolate in some other way, or combine the vertex scalar values? I'd love some help with this. A full testcase can be downloaded HERE

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  • Equivalent of CGPoint with integers?

    - by Ivan Vucica
    Cheers, I like strict typing in C. Therefore, I don't want to store a 2D vector of floats if I specifically need integers. Is there an Apple-provided equivalent of CGPoint which stores data as integers? I've implemented my type Vector2i and its companion function Vector2iMake() à la CGPoint, but something deep in me screams that Apple was there already.

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  • Generate colors between red and green for a power meter?

    - by Simucal
    I'm writing a java game and I want to implement a power meter for how hard you are going to shoot something. I need to write a function that takes a int between 0 - 100, and based on how high that number is, it will return a color between Green (0 on the power scale) and Red (100 on the power scale). Similar to how volume controls work: What operation do I need to do on the Red, Green, and Blue components of a color to generate the colors between Green and Red? So, I could run say, getColor(80) and it will return an orangish color (its values in R, G, B) or getColor(10) which will return a more Green/Yellow rgb value. I know I need to increase components of the R, G, B values for a new color, but I don't know specifically what goes up or down as the colors shift from Green-Red. Progress: I ended up using HSV/HSB color space because I liked the gradiant better (no dark browns in the middle). The function I used was (in java): public Color getColor(double power) { double H = power * 0.4; // Hue (note 0.4 = Green, see huge chart below) double S = 0.9; // Saturation double B = 0.9; // Brightness return Color.getHSBColor((float)H, (float)S, (float)B); } Where "power" is a number between 0.0 and 1.0. 0.0 will return a bright red, 1.0 will return a bright green. Java Hue Chart: Thanks everyone for helping me with this!

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  • How can I "best fit" an arbitrary cairo (pycairo) path?

    - by Daniel Straight
    It seems like given the information in stroke_extents() and the translate(x, y) and scale(x, y) functions, I should be able to take any arbitrary cairo (I'm using pycairo) path and "best fit" it. In other words, center it and expand it to fill the available space. Before drawing the path, I have scaled the canvas such that the origin is the lower left corner, up is y+, right is x+, and the height and width are both 1. Given these conditions, this code seems to correctly scale the path: # cr is the canvas extents = cr.stroke_extents() x_size = abs(extents[0]) + abs(extents[2]) y_size = abs(extents[1]) + abs(extents[3]) cr.scale(1.0 / x_size, 1.0 / y_size) I cannot for the life of me figure out the translating though. Is there a simpler approach? How can I "best fit" a cairo path on its canvas? Please ask for clarification if anything is unclear in this question.

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  • Tracking object entries when "playing" a Windows Enhanced Metafile

    - by lzcd
    One of my current projects requires that I work out what colours are being used in an EMF file. I have been able to successfully whip up a file parser in C# that notes all references to colours... but haven't had any luck tracking which objects are in use across the entire file so I can apart colours that are referenced from colours that are used to paint on screen. The older style WMF files are easy as the object library starts at zero and one can simply track each "Create Object" style command... but EMF files are proving to be trickier as there seems to be preexisting entries in the library (if the "Select Object" commands I'm seeing are to be believed). Would anyone be able to either enlighten me on how to track objects in the library correctly with EMF files... or suggest an easier alternative to work out which colours are actually being used in the file (as opposed to just being defined)?

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  • OpenGL Color Interpolation across vertices

    - by gutsblow
    Right now, I have more than 25 vertices that form a model. I want to interpolate color linearly between the first and last vertex. The Problem is when I write the following code glColor3f(1.0,0.0,0.0); vertex3f(1.0,1.0,1.0); vertex3f(0.9,1.0,1.0); . .`<more vertices>; glColor3f(0.0,0.0,1.0); vertex3f(0.0,0.0,0.0); All the vertices except that last one are red. Now I am wondering if there is a way to interpolate color across these vertices without me having to manually interpolate color natively (like how opengl does it automatically) at each vertex since, I will be having a lot more number of colors at various vertices. Any help would be extremely appreciated. Thank you!

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  • getting window screenshot windows API

    - by Oliver
    Hi, I am trying to make a program to work on top of an existing GUI to annotate it and provide extra calculations and statistical information. I want to do this using image recognition, as I have learned a fair amount about this in University using Matlab and similar things. I can get a handle to the window I want to perform image recognition on, but I don't know how to turn that handle into an image of that window, and all its visible child windows. I suppose I am looking for something like the screenshot function, but restricted to a single window. How would I go about doing this? I suppose I'd need something like a .bmp to mess about with. Also, it would have to be efficient enough that I could call it several times a second without my PC grinding to a halt. Hopefully this isn't an obvious question, I typed some things into google but didn't get anything related.

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  • How to write text(using CGContextShowTextAtPoint) on graph x and y-axis intervals points?

    - by Rajendra Bhole
    I developed graph using NSObject class and using CGContext method. The following code displaying dynamically in X and Y-axis intervals, CGContextSetRGBStrokeColor(ctx, 2.0, 2.0, 2.0, 1.0); CGContextSetLineWidth(ctx, 2.0); CGContextMoveToPoint(ctx, 30.0, 200.0); CGContextAddLineToPoint(ctx, 30.0, 440.0); for(float y = 400.0; y >= 200.0; y-=30) { CGContextSetRGBStrokeColor(ctx, 2.0, 2.0, 2.0, 1.0); CGContextMoveToPoint(ctx, 28, y); CGContextAddLineToPoint(ctx, 32, y); CGContextStrokePath(ctx); //CGContextClosePath(ctx); } CGContextMoveToPoint(ctx, 10, 420.0); CGContextAddLineToPoint(ctx, 320, 420.0); //CGContextAddLineToPoint(ctx, 320.0, 420.0); //CGContextStrokePath(ctx); for(float x = 60.0; x <= 260.0; x+=30) { CGContextSetRGBStrokeColor(ctx, 2.0, 2.0, 2.0, 1.0); CGContextMoveToPoint(ctx, x, 418.0); CGContextAddLineToPoint(ctx, x, 422.0); CGContextStrokePath(ctx); CGContextClosePath(ctx); } I want to write the dynamic text on the X and Y-axis lines near the intervals (like X-axis is denoting number of days per week and Y-axis denoting something per someting)? Thanks.

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  • OpenGL 2D Texture Mapping problem.

    - by gutsblow
    Hi there, I am relatively new to OpenGL and I am having some issues when I am rendering an image as a texture for a QUAD which is as the same size of the image. Here is my code. I would be very grateful if someone helps me to solve this problem. The image appears way smaller and is squished. (BTW, the image dimensions are 500x375). glGenTextures( 1, &S_GLator_InputFrameTextureIDSu ); glBindTexture(GL_TEXTURE_2D, S_GLator_InputFrameTextureIDSu); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); glTexImage2D( GL_TEXTURE_2D, 0, 4, S_GLator_EffectCommonData.mRenderBufferWidthSu, S_GLator_EffectCommonData.mRenderBufferHeightSu, 0, GL_RGBA, GL_UNSIGNED_BYTE, dataP); glBindTexture(GL_TEXTURE_2D, S_GLator_InputFrameTextureIDSu); glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, S_GLator_EffectCommonData.mRenderBufferWidthSu, S_GLator_EffectCommonData.mRenderBufferHeightSu, GL_RGBA, GL_UNSIGNED_BYTE, bufferP); //set the matrix modes glMatrixMode( GL_PROJECTION ); glLoadIdentity(); //gluPerspective( 45.0, (GLdouble)widthL / heightL, 0.1, 100.0 ); glOrtho (0, 1, 0, 1, -1, 1); // Set up the frame-buffer object just like a window. glViewport( 0, 0, widthL, heightL ); glDisable(GL_DEPTH_TEST); glClearColor( 0.0f, 0.0f, 0.0f, 0.0f ); glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); glMatrixMode( GL_MODELVIEW ); glLoadIdentity(); glBindTexture( GL_TEXTURE_2D, S_GLator_InputFrameTextureIDSu ); //Render the geometry to the frame-buffer object glBegin(GL_QUADS); //input frame glColor4f(1.f,1.f,1.f,1.f); glTexCoord2f(0.0f,0.0f); glVertex3f(0.f ,0.f ,0.0f); glTexCoord2f(1.0f,0.0f); glVertex3f(1.f ,0.f,0.0f); glTexCoord2f(1.0f,1.f); glVertex3f(1.f ,1.f,0.0f); glTexCoord2f(0.0f,1.f); glVertex3f(0.f ,1.f,0.0f); glEnd();

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  • Intersection of line with cube and knowing the point of intersection.

    - by Raj
    Hello everyone, description 1.lines are originating from origin(0,0,0). 2.lines are at some random angle to the Normal of Top face of teh cube. 3.if the lines are intersecting cube , calculate the intersection point. 4.mainly i wan to know how much distance ,line traveled inside the cube. I dont know exactly which approach should i take , i will be pleased and thankful if someone could guied me to the right direction, to use OpenGL, DirectX or some other library, for C# . some example or sample will be appriciated.

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  • Is it possible to use AnimateWindow with AW_BLEND when using a layered window?

    - by wkf
    I am displaying a window using UpdateLayeredWindow and would like to add transition animations. AnimateWindow works if I use the slide or roll effects (though there is some flickering). However, when I try to use AW_BLEND to produce a fade effect, I not only lose any translucency after the animation (per-pixel and on the entire image), but a default window border also appears. Is there a way to prevent the border from appearing?

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