core-graphics

问题 Just wondering how to draw an ellipse using CoreGraphics. 回答1: CGContextStrokeEllipseInRect or CGContextFillEllipseInRect 来源： https://stackoverflow.com/questions/3231902/how-do-i-draw-a-simple-ellipse-using-coregraphics-on-the-iphone-specifically-ip

问题 I'm blending two images in my iPhone app, using the HardLight blend mode of the top image. It looks something like this: UIGraphicsBeginImageContext(size); [sourceImage drawInRect:rectangle blendMode:kCGBlendModeNormal alpha:1.0]; [effectOverlay drawInRect:rectangle blendMode:kCGBlendModeHardLight alpha:0.75]; mainImage.image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); It works fine. However, the blown-out highlights in the image appear with a weird color

问题 In my OpenGL-ES 1.1 based app, I'm using CALayer s as a source for OpenGL textures. Those CALayer s comprise of CGImage s and text rendered through CoreGraphics. Another OpenGL texture source is a screenshot of a UIView taken using -[CALAyer renderInContext:] and UIGraphicsGetImageFromCurrentImageContext . Currently, I'm running completely on the main thread. The latter case in particular is pretty bad because it halts the OpenGL rendering for the whole time it takes to create the UIView and

问题 I'm working on coretext in iOS. I have implemented a custom UIView by replacing -drawRect method with the following code: - (void)drawRect:(CGRect)rect { [super drawRect:rect]; CGRect frameRect=CGRectMake(50, 200, 80, 15); // NSString *textToDraw=@"A-BCDEFGHIJKLM"; // NSString *textToDraw=@"abc"; // NSString *textToDraw=@"ABCDEFGHIJKLMNOPQRST"; NSString *textToDraw=@"A-BCDEFGHIJ"; // NSString *textToDraw=@"A-BCDEFGHI"; CFStringRef stringRef = (__bridge CFStringRef)textToDraw;

问题 I'm using this code: CGRect screenRect = [[UIScreen mainScreen] bounds]; CGFloat screenWidth = screenRect.size.width; CGFloat screenHeight = screenRect.size.height; NSString * text = @"text"; CGContextSetFillColorWithColor(context, [UIColor colorWithRed:1 green:1 blue:1 alpha:RETICLE_ALPHA].CGColor); [text drawAtPoint:CGPointMake(screenWidth/2, screenHeight/2) withFont: [UIFont systemFontOfSize:22.0]]; to create a centered "text" for iOS. But I'm not sure how to edit the code above to really

问题 I'm creating an image offscreen using a context from CGBitmapContextCreate() . While drawing text, I tried to use the: CGContextSetTextMatrix(contextRef, CGAffineTransformMake(1.0, 0.0, 0.0, -1.0, 0.0, 0.0)); but my text was still upside down. If I used the standard transforms it was correct: CGContextTranslateCTM(contextRef, 0.0, contextRect.size.height); CGContextScaleCTM(contextRef, 1.0, -1.0); My question is should the CGContextSetTextMatrix work for an offscreen bitmap? Maybe I was doing

问题 I'm creating an image offscreen using a context from CGBitmapContextCreate() . While drawing text, I tried to use the: CGContextSetTextMatrix(contextRef, CGAffineTransformMake(1.0, 0.0, 0.0, -1.0, 0.0, 0.0)); but my text was still upside down. If I used the standard transforms it was correct: CGContextTranslateCTM(contextRef, 0.0, contextRect.size.height); CGContextScaleCTM(contextRef, 1.0, -1.0); My question is should the CGContextSetTextMatrix work for an offscreen bitmap? Maybe I was doing

问题 I'm running that method in quick succession as fast as I can, and the faster the better, so obviously if CGDataProviderCopyData() is actually copying the data byte-for-byte, then I think there must be a faster way to directly access that data...it's just bytes in memory. Anyone know for sure if CGDataProviderCopyData() actually copies the data? Or does it just create a new pointer to the existing data? 回答1: The bytes are copied. Internally a CFData is created (CFDataCreate) with the content

问题 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

问题 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