core-graphics

this is my first question here, so hello everyone. I have spent some time now wrapping my mind around the following problem and could not come up with a solution. I'd be happy if someone could point me in the right direction. I'm using CGContext to draw various layers of graphical representations of live data which should be refreshed at a reasonable framerate of at least 50fps. I want to use a static image as a background. Re-drawing this image using the context for every cycle significantly slows down the frame-rate. I thought about just using UIImageView to display the image once. The

My app uses core graphics for custom finger paint drawing. I allow the user to change the alpha of the line and a new line is continuously drawn on touches moved. When I make the alpha lower than 1.0 the point of overlap is darker than the rest of the line. I know why this occurs but how can I stop this? Kris Van Bael I suppose you want a single stroke not to darken itself, but still to darken previous strokes (that's how most painting apps work). For this to work, you need two views/buffers, one for the 'current background' and one for the current stroke. Merge the latter with the background

I am drawing an arc that is an almost complete circle: CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor); CGMutablePathRef path = CGPathCreateMutable(); CGPathMoveToPoint(path, NULL, centerPoint.x, centerPoint.y); CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, radius, (float)(3.0f * M_PI_2), radians, !clockwise); CGPathCloseSubpath(path); CGContextAddPath(context, path); CGContextFillPath(context); CGPathRelease(path); I have an arc like path that is an almost complete circle. In this code it is all one color, however, I want one end to be a solid white color and

I'm running into a thorny problem with posting an event from an event tap. I'm tapping for NSSystemDefined at kCGHIDEventTap, then replacing the event with a new one. The problem I'm running in to is that depending on how I post the event, it's being seen only by some applications. My test applications are Opera, Firefox, Quicksilver, and Xcode. Here are the different techniques I've tried within my event tap callback, with results. I'm expecting an action (the "correct response") from each app; "system beep" means the nothing-is-bound-to-that-key system sound. Create a new event, and return

Thanks to some help on StackOverflow, I am currently animating a path in CAShapeLayer to make a triangle that points from a moving sprite to another moving point on the screen. Once the animation completes, the triangle disappears from the screen. I am using very short durations because this code is being fired every .1 of second for each of the sprites. The result is the red triangle tracks correctly, but it rapidly flashes or isn't there entirely. When I crank up the the duration, I can the see the triangle stay longer. What can I do to get the triangle to stay on the screen, with it's

I'm trying to process some imagedata which comes directly from the device camera. In order to understand the CGImage structure, I'm using a buffer to create an image which doesn't work right for me (I know that I shouldn't use C code within Obj-C Code, it's just for understanding). The code is as follows: int *outBuf = malloc(sizeof(int) * width * height); for (int i = 0; i < width * height;i ++) { outBuf[i] = (((float)i) / ((float) width * height)) * 255.f; } CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); CGContextRef ctx = CGBitmapContextCreate(outBuf, width, height, 8, width *

Without my doing anything to request upside down text, CGContextShowText is drawing it in that fashion. It is a mirror image vertically of what it should be. float font_size = 19.; CGContextSelectFont (context, "Helvetica", font_size, kCGEncodingMacRoman); CGContextSetTextDrawingMode (context, kCGTextFill); CGContextSetRGBStrokeColor (context, 255, 0, 0, 0); CGContextSetRGBFillColor (context, 255, 0, 0, 0); CGContextSetTextPosition (context, x, y); CGContextShowText (context, cstring, strlen(cstring)); How can I fix this? Also why is this the default drawing mode? Thanks. This "upsidedownness"

I´m trying to get a list of windows on OSX from the core-graphics API with Swift (to capture an image of them later on). After some research I found the CGWindowListCopyWindowInfo Objective-C API call with the following signature: CFArrayRef CGWindowListCopyWindowInfo( CGWindowListOption option, CGWindowID relativeToWindow ); Parameters option: The options describing which window dictionaries to return. Typical options let you return dictionaries for all windows or for windows above or below the window specified in the relativeToWindow parameter. For more information, see Window List Option