This should be a simple one, basically I have a few paths drawn with core graphics, and I want to be able to rotate them (for convenience). I've tried using CGContextRotateCTM(context); but it's not rotating anything. Am I missing something? Here's the source for drawRect - (void)drawRect:(CGRect)rect { CGContextRef context = UIGraphic...
Can someone tell me what I am doing wrong here? I use this method to flip through pages in a PDF. But something in the code seems to not be released properly because every-time I pull a PDF page that contains an image my memory footprint increases. I am fairly new to CoreGraphics, and can't for the life of me figure out where this method...
Hello, I have a method that needs to parse through a bunch of large PNG images pixel by pixel (the PNGs are 600x600 pixels each). It seems to work great on the Simulator, but on the device (iPad), i get an EXC_BAD_ACCESS in some internal memory copying function. It seems the size is the culprit because if I try it on smaller images, eve...
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-i...
Hi All, I want to draw a sinusodial wave which varies with time on a UIView. What are the approaches should i take ? Any sample code is there ?? ...
Hi All, How to draw audio waveforms on a UIView ? ...
I'm looking for a way to draw a curve (perhaps a parametric function?) into a CGContext The best example which I can think of is the Adobe Ideas iPad application. As the user drags their finger, the application draws lines for every touchesMoved: using CGContextAddLineToPoint. After the user picks up their finger at touchesEnded:, the a...
I am executing the following, which I have derived from a few different tutorials (Just a single render pass, initialisation code not shown but works fine for untextured primitives): glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrthof(0, xSize, 0, ySize, -1.0f, 1.0f); glMatrixMode(GL_MODELVIEW); glColor4f(1.0f, 1.0f, 1.0f, 1.0f); g...
It is quite hard to tell so I upload an image to show my problem: http://i42.tinypic.com/2eezamo.jpg Basically in drawRect, I will draw the line from touchesMoved as finger touches and I will call "needsDisplayInRect" for redraw. But I found that the first line is done, the second line will clear the rect part, so some previouse drawing...
I use CGContexts to allow the user to draw in my application, here's an example: CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); CGContextSetLineWidth(UIGraphicsGetCurrentContext(), size); CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(),r,g,b,a); I want the user to have an "eraser" tool that a...
In my code I'm trying to show a UIWebView as a page is loading, and then, when it's done, capture an image from the web view to cache and display later (so I don't have to reload and render the web page). I have something along the lines of: CGContextRef context = CGBitmapContextCreate(…); [[webView layer] renderInContext:context]; CG...
Hello, So I have a spritesheet in png format, and have already worked out the coordinates for what I want to display. I'm trying to create a method that will return a UIImage when passed the location information on the spritesheet. I'm just not sure how to use the CGContext stuff along with the the coordinates to return an UIImage. I ...
Hi I have a CALayer tree hierarchy A B C D where A is the view's root layer (and I create and add B,C and D layers. I am using the same delegate method `- (void) drawLayer:(CALayer *) theLayer inContext:(CGContextRef)context to provide content to each of these layers (implemented through a switch statement in the above method...
I've taken a look at this question: http://stackoverflow.com/questions/962827/uiimage-shadow But the accepted answer didn't work for me. What I'm trying to do is take a UIImage and add a shadow to it, then return a whole new UIImage, shadow and all. This is what I'm trying: - (UIImage*)imageWithShadow { CGColorSpaceRef colourSpa...
Error: CGBitmapContextCreate: invalid data bytes/row: should be at least 400 for 8 integer bits/component, 3 components, kCGImageAlphaNoneSkipFirst. Error: CGContextDrawImage: invalid context Error: CGBitmapContextCreateImage: invalid context Currently, I have in application that runs perfectly in OS 4.0, but I have been trying to get...
Hi all, In the process of updating my iPad app I've been attempting to draw a page from an existing PDF document into a Core Graphics context then save it as a new PDF, but am having difficulty getting the text to display properly. Images in the newly-created PDF look great, but text rarely appears correctly: more often that not it appe...
My big picture goal is to have a grey field over an image, and then as the user rubs on that grey field, it reveals the image underneath. Basically like a lottery scratcher card. I've done a bunch of searching through the docs, as well as this site, but can't find the solution. The following is just a proof of concept to test "erasing...
I am having some troubles using the CGContext with an iPhone app. I am trying to draw several lines with different colors, but all the lines always end up having to color, which was used last. I tried several approaches I could think of, but haven't been lucky. I set up a small sample project to deal with that issue. This is my code, I...
I have a CGBitmapContext (bitmapContext) and I would like to draw some rectangle part (rect) of it to the current CGContext (context). Right now I do that way: CGContextRef context = UIGraphicsGetCurrentContext(); CGImageRef cgImage = CGBitmapContextCreateImage(bitmapContext); CGContextClipToRect(context, rect); CGContextDrawImage(cont...
I have a UIImageView within a UIScrollView which I have enabled the user to perform any number of flip and rotation operations on. I have this all working which allows the user to zoom, pan, flip and rotate. Now I want to be able to save the final image out to a png. however it is doing my head in trying to work this out... I have seen...