I'm currently drawing on the screen. I get smooth lines, I can change the color of my drawings. But I can't find how to apply a shadow to that line.
To draw it, I use :
[path strokeWithBlendMode:[path blendMode] alpha:1.0];
I saw that I could use CGContextSetShadowWithColor() but even though, I'm not sure how to use it since here's what's said in the CGPath reference for strokeWithBlendMode:
This method automatically saves the current graphics state prior to
drawing and restores that state when it is done, so you do not have to
save the graphics state yourself.
So I don't really know where to put that CGContextSetShadowWithColor() or anything else if I can use it.
Regards
If you want to use CGContextSetShadowwithColor() then you will need to change the way to draw your bezierpath to the view so that you draw the CGPath representation to the CGContext. An example is below:
UIBezierPath *path; // this is your path as before
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextAddPath(context, path.CGPath);
CGContextSetLineWidth(context, 2.0);
CGContextSetBlendMode(context, path.blendMode);
CGContextSetShadowWithColor(context, CGSizeMake(1.0, 1.0), 2.0, [UIColor blackColor].CGColor);
CGContextStrokePath(context);
Another way you could do this is to create a new CAShapeLayer and draw you path to that by setting it as the path property. This will easily allow you to add a shadow that will only shadow your path.
Related
I'm new to context concept in Apple iOS programming. Currently, I'm thinking in views. I want to draw an arc using the easiest method possible, and then I found this question and answer. But then I'm confused with context concept. I thought to draw something, I will need to call the drawing function and supply the view where I want the drawing function to draw. But in there, I got confused with UIGraphicsGetCurrentContext(). What "current context" is that? Is it the UIScreen.mainScreen()? How if I want to set the "current context" to a view inside a UICollectionViewCell, so that all the pixel drawn will be relative to the view? Can I do that?
The way you draw in CocoaTouch is to subclass UIView to create a custom view and implement the drawRect:(CGRect)rect method. Put your drawing code inside drawRect. Something like:
-(void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGPathRef path = CGPathCreateWithRect(rect, NULL);
[[UIColor blueColor] setStroke];
CGContextSetLineWidth(context, 4.0);
CGContextAddPath(context, path);
CGContextDrawPath(context, kCGPathFillStroke);
CGPathRelease(path);
}
You can put your custom UIView inside of a UICollectionViewCell if you want.
I am using a UIbezierpath to draw for my Project. I am using colors to draw. When I draw on same points, the color becomes darken.(i.e drawing on the same place will normally). I want to maintain the brush color though on overwrite.
Any help will be appreciated!!!!
Let's try below method,
- (void)drawRect:(CGRect)rect
{
CGContextSetFillColorWithColor(UIGraphicsGetCurrentContext(),self.backgroundColor.CGColor);
CGContextFillRect(UIGraphicsGetCurrentContext(), rect); // This line will clear your existing drawing
// Line Drawing code
}
OR
UIBezierPath * path = [UIBezierPath bezierPathWithRect:(CGRect){CGPointZero, newSize}]; // newSize will be your size of the Eraser
[[UIColor clearColor] setFill];
[path fill];
Please refer this link as well to make paint and erase.
Thanks!
I want to achieve the shape shown in image using UIBezier Path, and too the shape is filled with blocks in image it shows one block is filled, how to achieve this.
I have tried the following code taken from here
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:CGPointMake(0, 10)];
[path addQuadCurveToPoint:CGPointMake(200, 10) controlPoint:CGPointMake(100, 5)];
[path addLineToPoint:CGPointMake(200, 0)];
[path addLineToPoint:CGPointMake(0, 0)];
[path closePath];
Thanks.
It looks to me like both the outline and also each block has the same shape. What you would probably do is to make one shape for the outline, and stroke it, and one shape for each cell and fill it.
Creating the shape
Each shape could be created something like this (as I've previously explained in this answer). It's done by stroking one path (the orange arc) which is a simple arc from one angle to another to get another path (the dashed outline)
Before we can stroke the path we to create it. CGPath's work just like UIBezierPath but with a C API. First we move to the start point, then we add an arc around the center from the one angle to another angle.
CGMutablePathRef arc = CGPathCreateMutable();
CGPathMoveToPoint(arc, NULL,
startPoint.x, startPoint.y);
CGPathAddArc(arc, NULL,
centerPoint.x, centerPoint.y,
radius,
startAngle,
endAngle,
YES);
Now that we have the centered arc, we can create one shape path by stroking it with a certain width. The resulting path is going to have the two straight lines (because we specify the "butt" line cap style) and the two arcs (inner and outer). As you saw in the image above, the stroke happens from the center an equal distance inwards and outwards.
CGFloat lineWidth = 10.0;
CGPathRef strokedArc =
CGPathCreateCopyByStrokingPath(arc, NULL,
lineWidth,
kCGLineCapButt,
kCGLineJoinMiter, // the default
10); // 10 is default miter limit
You would do this a couple of times to create one path for the stroked outline and one path for each cell.
Drawing the shape
Depending on if it's the outline or a cell you would either stroke it or fill it. You can either do this with Core Graphics inside drawRect: or with Core Animation using CAShapeLayers. Choose one and don't between them :)
Core Graphics
When using Core Graphics (inside drawRect:) you get the graphics context, configure the colors on it and then stroke the path. For example, the outline with a gray fill color and a black stroke color would look like this:
I know that your shape is filled white (or maybe it's clear) with a light blue stroke but I already had a gray and black image and I didn't want to create a new one ;)
CGContextRef c = UIGraphicsGetCurrentContext();
CGContextAddPath(c, strokedArc); // the path we created above
CGContextSetFillColorWithColor(c, [UIColor lightGrayColor].CGColor);
CGContextSetStrokeColorWithColor(c, [UIColor blackColor].CGColor);
CGContextDrawPath(c, kCGPathFillStroke); // both fill and stroke
That will put something like this on screen
Core Animation
The same drawing could be done with a shape layer like this:
CAShapeLayer *outline = [CAShapeLayer layer];
outline.fillColor = [UIColor lightGrayColor].CGColor;
outline.strokeColor = [UIColor blackColor].CGColor;
outline.lineWidth = 1.0;
outline.path = strokedArc; // the path we created above
[self.view.layer addSublayer: outline];
In my custom control I have defined a few CGMutablePathRefs with the needed lines and arcs to draw my control; one draws the overall fill shape and others provide specular highlights. I have also defined two CGMutablePathRefs which contain the paths needed as clipping masks for the active and inactive state of the control.
What I'm struggling with is applying the clipping paths. I have previously used clipping paths for applying gradients to an image, but those drawing commands were of the CGContext... variety, not the CGPath... variety.
For testing purposes I have removed the specular highlight drawing aspects, just trying to get a large path clipped to a smaller path. This is what I had been testing with:
- (void)drawRect:(CGRect)rect
{
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextBeginPath(ctx);
CGContextAddPath(ctx, inactiveClip);
CGContextClosePath(ctx);
CGContextClip(ctx);
CGContextAddPath(ctx, frontFace);
CGContextSetLineWidth(ctx, 1.0);
CGContextSetFillColorWithColor(ctx, [[UIColor blackColor] CGColor]);
CGContextFillPath(ctx);
}
By putting the clipping command before any drawing, I thought I was saying to CoreGraphics, "Here's the region you should actually draw into."
Alas, nothing is drawn.
So assuming I had that ordering backwards I tried:
- (void)drawRect:(CGRect)rect
{
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextAddPath(ctx, frontFace);
CGContextSetLineWidth(ctx, 1.0);
CGContextSetFillColorWithColor(ctx, [[UIColor blackColor] CGColor]);
CGContextFillPath(ctx);
CGContextBeginPath(ctx);
CGContextAddPath(ctx, inactiveClip);
CGContextClosePath(ctx);
CGContextClip(ctx);
}
This was to say to CoreGraphics, "Okay before you actually color bits, check them against this clipping region."
Alas, nothing is clipped.
Since it is the case that my clipping path uses some of the same points and control points, in the same order, as the fill path, I have also replaced the call to CGContextClip with a call to CGContextEOClip to see if I was really struggling with the even-odd rule, but that doesn't seem to have had any visual affect.
I don't really know if I needed to bracket the CGContextAddPath call with CGContextBeginPath/CGContextClosePath calls, but what I was trying to do was minimize the differences between Apple's example code and my code. In theirs they do their CGContext... drawing calls between begin/close calls so I was too.
What am I misunderstanding here?
I'm trying to programmatically recreate the indented button look that can be seen on a UINavigationBarButton. Not the shiny two tone look or the gradient, just the perimeter shading:
It looks like an internal dark shadowing around the entire view perimeter, slightly darker at the top? And then an external highlighting shadow around the lower view perimeter.
I've played a bit with Core Graphics, and experimented with QuartzCore and shadowing with view.layer.shadowRadius and .shadowOffset, but can't even get the lower highlighting to look right. I'm also not sure where to start to achieve both a dark shadowing with internal offset and a light shadowing with external offset.
It seems as though you want a border that looks looks like a shadow. Since the shadow appears to some sort of gradient, setting a border as a gradient won't be possible at first glance. However, it is possible to create a path that represents the border and then fill that with a gradient. Apple provides what seems to be a little known function called CGPathCreateCopyByStrokingPath. This takes a path (say, a rounded rect, for example) and creates a new path that would be the stroke of the old path given the settings you pass into the function (like line width, join/cap setting, miter limit, etc). So lets say you define a path (this isn't exactly what Apple provides, but's it's similar):
+ (UIBezierPath *) bezierPathForBackButtonInRect:(CGRect)rect withRoundingRadius:(CGFloat)radius{
UIBezierPath *path = [UIBezierPath bezierPath];
CGPoint mPoint = CGPointMake(CGRectGetMaxX(rect) - radius, rect.origin.y);
CGPoint ctrlPoint = mPoint;
[path moveToPoint:mPoint];
ctrlPoint.y += radius;
mPoint.x += radius;
mPoint.y += radius;
if (radius > 0) [path addArcWithCenter:ctrlPoint radius:radius startAngle:M_PI + M_PI_2 endAngle:0 clockwise:YES];
mPoint.y = CGRectGetMaxY(rect) - radius;
[path addLineToPoint:mPoint];
ctrlPoint = mPoint;
mPoint.y += radius;
mPoint.x -= radius;
ctrlPoint.x -= radius;
if (radius > 0) [path addArcWithCenter:ctrlPoint radius:radius startAngle:0 endAngle:M_PI_2 clockwise:YES];
mPoint.x = rect.origin.x + (10.0f);
[path addLineToPoint:mPoint];
[path addLineToPoint:CGPointMake(rect.origin.x, CGRectGetMidY(rect))];
mPoint.y = rect.origin.y;
[path addLineToPoint:mPoint];
[path closePath];
return path;
}
This returns a path similar to Apple's back button (I use this in my app). I have added this method (along with dozens more) as a category to UIBezierPath.
Now lets add that inner shadow in a drawing routine:
- (void) drawRect:(CGRect)rect{
UIBezierPath *path = [UIBezierPath bezierPathForBackButtonInRect:rect withRoundingRadius:5.0f];
//Just fill with blue color, do what you want here for the button
[[UIColor blueColor] setFill];
[path fill];
[path addClip]; //Not completely necessary, but borders are actually drawn 'around' the path edge, so that half is inside your path, half is outside adding this will ensure the shadow only fills inside the path
//This strokes the standard path, however you might want to might want to inset the rect, create a new 'back button path' off the inset rect and create the inner shadow path off that.
//The line width of 2.0f will actually show up as 1.0f with the above clip: [path addClip];, due to the fact that borders are drawn around the edge
UIBezierPath *innerShadow = [UIBezierPath bezierPathWithCGPath: CGPathCreateCopyByStrokingPath(path.CGPath, NULL, 2.0f, path.lineCapStyle, path.lineJoinStyle, path.miterLimit)];
//You need this, otherwise the center (inside your path) will also be filled with the gradient, which you don't want
innerShadow.usesEvenOddFillRule = YES;
[innerShadow addClip];
//Now lets fill it with a vertical gradient
CGContextRef context = UIGraphicsGetCurrentContext();
CGPoint start = CGPointMake(0, 0);
CGPoint end = CGPointMake(0, CGRectGetMaxY(rect));
CGFloat locations[2] = { 0.0f, 1.0f};
NSArray *colors = [NSArray arrayWithObjects:(id)[UIColor colorWithWhite:.7f alpha:.5f].CGColor, (id)[UIColor colorWithWhite:.3f alpha:.5f].CGColor, nil];
CGGradientRef gradRef = CGGradientCreateWithColors(CGColorSpaceCreateDeviceRGB(), (__bridge CFArrayRef)colors, locations);
CGContextDrawLinearGradient(context, gradRef, start, end, 0);
CGGradientRelease(gradRef);
}
Now this is just a simple example. I don't save/restore contexts or anything, which you'll probably want to do. There are things you might still want to do to make it better, like maybe inset the 'shadow' path if you want to use a normal border. You might want to use more/different colors and locations. But this should get you started.
UPDATE
There is another method you can use to create this effect. I wrote an algorithm to bevel arbitrary bezier paths in core graphics. This can be used to create the effect you're looking for. This is an example of how I use it in my app:
You pass to the routine the CGContextRef, CGPathRef, size of the bevel and what colors you want it to use for the highlight/shadow.
The code I used for this can be found here:Github - Beveling Algorithm.
I also explain the code and my methodology here: Beveling-Shapes in Core Graphics
Using the layer's shadow won't do it. You need both a light outer shadow and a dark inner shadow to get that effect. A layer can only have one (outer) shadow. (Also, layer shadows are redrawn dynamically, and force CPU-based rendering which kills performance.)
You'll need to do your own drawing with CoreGraphics, either in a view's drawRect: method or a layer's drawInContext: method. (Or you draw into an image context and then reuse the image.) Said drawing will mostly use CGContext functions. (I'll name some below, but this link has documentation for them all.)
For a round rect button, you might find it tedious to create the appropriate CGPath -- instead, you can use +[UIBezierPath bezierPathWithRoundedRect:cornerRadius:] and then the path's CGPath property to set the context's current path with CGContextAddPath.
You can create an inner shadow by setting a clipping path (see CGContextClip and related functions) to the shape of the button, setting up a shadow (see CGContextSetShadowWithColor and related functions), and then drawing around the outside of the shape you want shadowed. For the inner shadow, stroke (CGContextStrokePath) a round-rect that's a bit larger than your button, using a thick stroke width (CGContextSetLineWidth) so there's plenty of "ink" to generate a shadow (remember, this stroke won't be visible due to the clipping path).
You can create an outer shadow in much the same way -- don't use a clipping path this time, because you want the shadow to be outside the shape, and fill (CGContextFillPath) the shape of your button instead of stroking it. Note that drawing a shadow is sort of a "mode": you save the graphics state (CGContextSaveGState), setup a shadow, then draw the shape you want to see a shadow of (the shape itself isn't drawn when you're in this mode), and finally restore state (CGContextRestoreGState) to get out of "shadow mode". Since that mode doesn't draw the shape, only the shadow, you'll need to draw the shape itself separately.
There's an order to do this all in, too. It should be obvious if you think about the order in which you'd paint these things with physical media: First draw the outer shadow, then the button's fill, then the inner shadow. You might add a stroke after that if the inner shadow doesn't give you a pronounced enough outline.
There are a few drawing tools which can output source code for CoreGraphics: Opacity is one that I use. Be careful with these, though, as they code they generate may not be efficient.