I've made an iOS program that allows the user to draw a line on the screen with their finger. I used the touchesBegan, touchesMoved, and touchesEnded methods, along with creating a CGContext and drawing my line that way. I want the line to look as though it is beveled into the screen, almost as if it was carved. How would this be possible?
You can achieve a simple bevel by stroking your lines three times:
first, with a color brighter than the background at points p(x-1, y-1) relative to the actual line
then, your line color at the actual line position, points p(x, y)
then, brighter than the line color, but darker than the background at p(x+1, y+1)
You can think of this as a light shining onto your lines from above and to the left, making the lower coordinates brighter, passing over the bevel and having a little shadow cast on the higher coordinates.
Once you get the hang of thinking through the pseudo-3D geometry this way, you can create prettier bevels, including details inside the line. Those will take more strokes.
Related
When attempting to draw, if you first select Draw Circle then select Draw Rectangle then go to click on the map, instead of beginning the drawing and dragging the shape out, the shape gets an initial placement and the map drags instead. You can do the opposite as well (select Rectangle then Circle then click/drag).
You can see this behavior here: http://leaflet.github.io/Leaflet.draw/docs/examples/full.html
Draw Circle the click/drag works Fine. Draw Rectangle then click/drag works fine. Draw Circle then Draw Rectangle then click/drag causes map to begin dragging instead of shape.
This does not seem to be an issue when going between Circle-Polygon or Rectangle-Polygon, only Circle-Rectangle.
I tried debugging to see if any errors or weird events were being thrown but no such luck.
I've been doing some research on online for a project I'm doing but so far haven't been able to quite get it working. I want to be able to slide my finger over a UIImage and delete part of it, kind of like an eraser. I'm able to draw lines on the screen but can't figure out how to do this. Any help would be greatly appreciated.
Can you mask the image and when you draw on it, it adds the lines to the mask (in white, rest of mask is black) and then it should make those spots transparent
http://iosdevelopertips.com/cocoa/how-to-mask-an-image.html
There are two parts to this problem-
a) Determining the curve along which the finger was moved
b) Drawing the curve (which is really a combination of short lines) with the white color
For part (a), have a look at UIPanGestureRecognizer. Using the touchesBegan: & touchesMoved methods, you will be notified every time the finger moves even the smallest distance, and the source and destination co-ordinates, say (x1, y1) & (x2, y2).
Part (b), As you know how to draw a line, now you need to draw a line from the source to the destination with the line's width (thickness) equal to the finger's. For that you can set the line's width using CGContextSetLineWidth.
I'm trying to build this:
Where the white background is in fact transparent. I know how to clip a CGPath to a set region, but this seems to be to other way around, since I need to substract regions from a filled CGPath.
I guess the right way to go would be to substract the whole outer-circles from the CGPath and then to draw smaller circles at my CGPoints, but I'm not sure how to execute the former. Can anyone point me in the right direction?
That's what I would do :
1) Draw your general line
2) CGContextSetBlendMode(context, kCGBlendModeClear) to "clear the context" when you draw.
3) Draw you bigger circles
4) CGContextSetBlendMode(context, kCGBlendModeNormal) to return to normal drawing
5) Draw your little circles.
You could instead start a transparency layer, draw the lines, then draw the larger transparent circles using the clear color, then draw the smaller black circles. Then when you finish the transparency layer, it will composite exactly what you want back onto the context.
Whenever I stroke a path with rounded corners on iPhone, the rounded corners are thicker than the rest of the stroked path. See here for what I mean:
rounded corner thickness http://img181.imageshack.us/img181/6372/screenshot20100320at123.png
Not sure why this happens, any ideas?
I agree with Peter Hosey's analysis that the outer half of your lines is getting clipped off, but my recommendation would be to move all the coordinates .5 pixels inward instead. This way your straight lines will be crisper (not antialiased across 2 screen pixels) as well.
I suspect that you're drawing within a rectangular clipping path; the corners fall completely within the rectangle, but the sides get cut in half: half inside the clipping path and so drawn, half outside and so clipped out.
Try adding the path to the clipping path before stroking it.
To do this, you will need to add the CGPath to the context's current path twice:
Add CGPath to current path.
Add current path to clipping path (thereby emptying current path).
Add CGPath to current path.
Stroke current path.
It just looks thicker. If you zoom in on it you will see what looks like a couple extra pixels of black is actually some pixels of gray caused by antialiasing.
Try turning off antialiasing to see if the result looks better.
Edit: Also the bottom right corner seems to have a drop shadow effect.
what's the best way to draw a (black) border around a line in quartz for iphone? I'm drawing lines on streets on map and if the line is yellow (which is a legit use case), it blends in with the street color. One thing I could do is lay my lines over a little thicker black line, but this doesn't sound very efficient.
One thing I could do is lay my lines over a little thicker black line, but this doesn't sound very efficient.
I'd say that's the best way to go, unless you have hard proof about it being inefficient. I doubt that though. Stroking and filling a custom shape is probably harder to implement, and likely less efficient stroking one path twice with two different stroke widths (and colors).