Issue with Drawing on UIImage - ios

Question

I am using the following code to Draw over an image. All the touch delegates are working, but the drawing is not rendered over the UIImage. Here is the code. I am not able to identify the issue. Thanks in advance.
- (id)initWithCoder:(NSCoder *)aDecoder {
if ((self = [super initWithCoder:aDecoder])) {
[self setupVariables];
}
return self;
}
- (void)drawPic:(UIImage *)thisPic {
myPic = thisPic;
[myPic retain];
[self setNeedsDisplay];
}
- (void)drawRect:(CGRect)rect {
float newHeight;
float newWidth;
float xPos;
float yPos;
float ratio;
if (myPic != NULL) {
ratio = myPic.size.height/460;
if (myPic.size.width/320 > ratio) {
ratio = myPic.size.width/320;
}
newHeight = myPic.size.height/ratio;
newWidth = myPic.size.width/ratio;
xPos = (320 - newWidth) / 2;
yPos = (460 - newHeight) / 2;
[myPic drawInRect:CGRectMake(xPos, yPos, newWidth, newHeight)];
}
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
NSArray *allTouches = [[event allTouches] allObjects];
if ([allTouches count] > 1) {
return;
}
else {
[self drawPoint:[allTouches objectAtIndex:0]];
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
NSArray *allTouches = [[event allTouches] allObjects];
if ([allTouches count] > 1) {
return;
}
else {
[self drawPoint:[allTouches objectAtIndex:0]];
self.previousPoint = nil;
self.point = nil;
}
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
NSArray *allTouches = [[event allTouches] allObjects];
if ([allTouches count] > 1) {
return;
}
else {
[self drawPoint:[allTouches objectAtIndex:0]];
self.previousPoint = nil;
self.point = nil;
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
NSArray *allTouches = [[event allTouches] allObjects];
if ([allTouches count] > 1) {
return;
}
else {
[self drawPoint:[allTouches objectAtIndex:0]];
}
}
- (void)dealloc {
CGContextRelease(offScreenBuffer);
[point release];
[previousPoint release];
[super dealloc];
}
- (void)setupVariables {
self.point = nil;
self.previousPoint = nil;
offScreenBuffer = [self setupBuffer];
}
- (CGContextRef)setupBuffer {
CGSize size = self.bounds.size;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL,size.width,size.height,8,size.width*4, colorSpace,kCGImageAlphaPremultipliedLast);
CGColorSpaceRelease(colorSpace);
CGContextTranslateCTM(context, 0, size.height);
CGContextScaleCTM(context, 1.0, -1.0);
return context;
}
- (void)drawToBuffer {
// Red Gr Blu Alpha
CGFloat color[4] = {0.0, 1.0, 0.0, 1.0};
if (self.previousPoint != nil) {
CGContextSetRGBStrokeColor(offScreenBuffer, color[0], color[1], color[2], color[3]);
CGContextBeginPath(offScreenBuffer);
CGContextSetLineWidth(offScreenBuffer, 10.0);
CGContextSetLineCap(offScreenBuffer, kCGLineCapRound);
CGContextMoveToPoint(offScreenBuffer, previousPoint.location.x, previousPoint.location.y);
CGContextAddLineToPoint(offScreenBuffer, point.location.x, point.location.y);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeColor);
CGContextDrawPath(offScreenBuffer, kCGPathStroke);
}
}
- (void)drawPoint:(UITouch *)touch {
PointLocation *currentLoc = [[PointLocation alloc] init];
currentLoc.location = [touch locationInView:self];
self.previousPoint = self.point;
self.point = currentLoc;
[self drawToBuffer];
[self setNeedsDisplay];
[currentLoc release];
}

Answer 1

It's very simple. You need to do all your drawing in drawRect: and you're only drawing the image in drawRect:, so that's why you only see the image.

Answer 2

-(void)drawPic:(UIImage *)thisPic {
//code for UIViewContentModeScaleAspectFit if needed
self.backgroundColor = [UIColor colorWithPatternImage:thisPic];
[self setNeedsDisplay];
}
Do Not use this in drawRect Method:
[myPic drawInRect:CGRectMake(xPos, yPos, newWidth, newHeight)];
Edit
- (void)drawRect:(CGRect)rect {
if (!myDrawing) {
// CGFloat scale = 0.5;
// CATransform3D transform = CATransform3DMakeScale(scale, scale, scale);
// [self layer].transform = transform;
myDrawing = [[NSMutableArray alloc] initWithCapacity:0];
self.lineOnOffArray = [[NSMutableArray alloc] initWithCapacity:0];
//arrPenThickness = [[NSMutableArray alloc] initWithCapacity:0];
}
CGContextRef ctx = UIGraphicsGetCurrentContext();
if ([myDrawing count] > 0) {
for (int i = 0 ; i < [myDrawing count] ; i++) {
NSArray *thisArray = [myDrawing objectAtIndex:i];
NSString *onOffFlag = [self.lineOnOffArray objectAtIndex:i];
if (([thisArray count] > 2) && (onOffFlag == #"1")){
float penT = [[arrPenThickness objectAtIndex:i] floatValue];
NSString* penC = [arrPenColors objectAtIndex:i];
NSArray *arr = [penC componentsSeparatedByString:#","];
float r = [[arr objectAtIndex:0]floatValue];
float g = [[arr objectAtIndex:1]floatValue];
float b = [[arr objectAtIndex:2]floatValue];
float a = [[arr objectAtIndex:3]floatValue];
CGContextSetRGBStrokeColor(ctx,
r/255.0,
g/255.0,
b/255.0,
a);
CGContextSetLineCap(ctx, kCGLineCapRound);
CGContextSetLineWidth(ctx, penT);
float thisX = [[thisArray objectAtIndex:0] floatValue];
float thisY = [[thisArray objectAtIndex:1] floatValue];
CGContextBeginPath(ctx);
for (int j = 2; j < [thisArray count] ; j+=2) {
CGContextMoveToPoint(ctx, thisX, thisY);
thisX = [[thisArray objectAtIndex:j] floatValue];
thisY = [[thisArray objectAtIndex:j+1] floatValue];
CGContextAddLineToPoint(ctx, thisX,thisY);
}
CGContextStrokePath(ctx);
}
}
}
}