Can anyone share a sample code to draw a non-rectangular part of a picture in delphi canvas?
You're looking for GDI paths. Start here, which explains what paths are in this context, and provides links on the left to explain the functionality available with them.
Google can turn up lots of examples of using paths in Delphi. If you can't find them, post a comment back here and I'll see what I can turn up for you.
Your question is pretty vague. But I suspect what you are looking for is clipping regions. Read up on them. Set the clipping region on the target device to the shape you want, and then draw the image onto the device. Only the part of the image that would be within the clipping region will be drawn.
Canvas.Ellipse(0, 0, 10, 20); // not a rectangle
I use so called runlists for this feature (generalized shapes and blitting them). I've seen them called warplists too. A shape is encoded as a runlist by defining it as a set of horizontal lines, and each line is two integer values (skip n pixels,copy n pixels).
This means you can draw entire lines, leaving you with only "height" draw operations.
So a rectangle is defined (the first "skip" pixels from top level corner to the left corner (xorg,yorg). The rectangle is width_rect wide, and width_pixels goes a line further. width_pixels can be wider than the width of the picture (alignment bytes)
(yorg*width_pixels+xorg , width_rect),
(width_pixels-width_rect , width_rect),
(width_pixels-width_rect , width_rect),
(width_pixels-width_rect , width_rect),
..
..
This way you can make your drawing routines pretty generic, and for simple, regular shapes (rects, circles) it takes only minor math to precalculate these lists. It simplified my shape handling enormously.
However I draw directly to bitmaps, not to canvasses, so I can't help with that part. A primitive that efficiently draws a row, and a way to extract a row from a graphic should be enough.
Related
I am currently trying to label lines that I draw in my Map (in my iOS app, but I guess it applies to all maps).
So what I currently am doing, I simplify my path so that I get rid of most small curves and then just draw my glyphs along that line. Currently that looks like this:
On some parts of the line that's already ok. If the line is quite straight and the corners aren't too spiky.
But in some parts you can just not read anything... So what are strategies to make that look nicer?
Does anybody know an algorithm or a strategy on how to make my path look like the red line here:
I am happy about any ideas on how to improve my drawing :)
I do it, in my commercial map rendering system, by finding a portion of the line without sharp corners. There is no way to make the label look good if it turns corners of a right angle or greater. If there's no section long enough I abbreviate the label (e.g., Link Road becomes Link Rd), or split it on to two lines. If there's still nowhere to draw the label I don't draw it.
Another thing that's important is to adjust the spacing so that ascenders and descenders don't clash, so you need to look at the bounding box of each adjacent pair of letters as you draw the text and add small amounts of space as necessary.
I don't bother to smooth my lines, as you suggest with your red line. It really doesn't seem to matter, at least with street labelling.
I was wondering what would be the best way to trim the "canvas" of an UIImage (pretty much like any image editor allows out there)
Now, the previous example is not a single UIImage. It's actually 2 UIViews. So clipping the superview against the blue box would do the trick, but I guess I am looking into the best possible way to do this. Given that there could be several blue boxes in the "canvas".
Is there a faster way than going through every pixel?
Thanks!
Thinking about it algorithmically, I would say no. You need to find the pixel that extends furthest to the left, right, top and bottom. Unless you look at every pixel from each direction you could miss non-transparent pixels.
You could speed things up if you figure out how to map your image into memory and then index into memory directly rather than using a high level function that fetches pixels. I would suggest searching from the top down (which would be sequential memory accesses) until you find a non-clear pixel. Then search from the end of the image backwards, which would give you the bottom-most pixel.
You would then want to limit your search from each side to only look starting at the first non-transparent pixel from the top and ending at the last non-transparent pixel on the bottom.
For anything other than a very large image this should take a fraction of a second.
Ok, I was being dumb. The union of the subviews is all I really needed, so its just a simple loop over the subviews and doing a CGRect union against their frames.
Say you have an array of points and an array of rects, and you want to do the following:
Draw a line that connects all the points in the point array, such that the parts of the line that are contained in at least one of the rects are not visible.
What is the best practice way to accomplish such a task in cocos2d ios?
This may sound like a hack, but if you are drawing the rectangles as well then you can draw them with a higher zOrder with respect to the line and the rectangles would could cover the parts of the lines they contain making those parts invisible.
Hope it helps!
I am trying to create a little arrow in the middle of one of the sides of a rectangle. ( like twitter tweet button).
Any ideas how to do it in fireworks cs4 ?
Thanks.
There are two ways of doing this and unlike all the answers presented here, they are going to give you more freedom if you want to resize your shape and yes the triangle will be a part of your final shape not a superimposed two shapes.
Extending a shape with Pen tool
First, start with a rectangle. It can have rounded corner, however you like it. Then, you can either ungroup it or selecting the subselection tool (the white arrow in the tools panel) and clicking on one of the corners, you can make it editable for the Pen tool. Then, choosing the Pen tool, click three times on the left side of the rectangle, creating three points apart from each other along the edge. Back to subselection tool and select the middle one. Clicking a few times on the left arrow key on your keyboard will make it go to left. Since we are altering the base shape, your new shape can receive further filters, stroke colors etc.
Adding your shape to another shape
Create your rectangle and triangle shape anyway you want to see it. Position triangle so the right of it is just over the left edge of the rectangle. Give it 1-2 px of intersection area if you want, you'll most likely play with this approach to have best results. Both objects selected, go to Modify menu and select Union under Combine Paths. This option will merge both shapes. Since, FW is going to approximate both object styles, you can a blurred stroke if you already had strokes in your objects. You can adjust it but some people thing the method described above is better since they are editing the original image so it's more constructive than guessing the outcome of this merging operation. As usual, using the Pen tool, you can refine your shape.
Have fun.
This question really doesn't belong on Stack Overflow, but I'll answer anyway, since I'm not sure where it should go.
If this is what you mean:
then try this:
Create a small triangle.
Rotate the triangle 90 degrees to the left, so that it looks like the arrow.
Position the triangle on the side of the rectangle.
Change the triangle's color to the same color as the rectangle.
Imagine you are drawing a map of county borders. You are given a set of polygons, one for each boundary, and you draw each polygon.
In places where two counties share a border you just end up drawing the border twice. In the absence of partial transparency effects, and with a solid pen, this is no problem.
But, on maps, borders of this kind are customarily shown by dash-dotted lines. In this case, situations like the one depicted below can happen:
Notice how the dash pattern, which normally is dash-dot-dot, gets screwed up where the two areas share a border. In this case, it happened to become a longdash-dot pattern, but in general it could do anything from coincidentally looking normal to creating a solid line.
How does/should map rendering software prevent artifacts of this kind from occuring?
The artifact is due the fact that the piece of border is drawn twice. Instead of trying to supress such artifacts, you could try to not draw border sections twice, by keeping a list of segments already drawn in memory, and if you encounter a stretch that's already drawn, you don't draw it again.
Your brush pattern colors some pixels black and leaves some pixels alone. Instead of leaving the pixel alone, can you set up your brush pattern to color those pixels white (or whatever your background color is)?
Another possibility is to always draw your county borders twice -- once with a solid white pattern, and again with the brush pattern of your choice.
I suppose they break their border lines into segments, then remove the overlaps.
This is mostly a geometric problem, not a drawing problem.
Instead of going with a dashed line, you could do it Zip-a-tone style, like this:
Zip-a-tone was this graphic art stuff that was basically a sticky sheet of plastic with a regular (printable) pattern of dots on it. To use it, you would lay a big sheet of it over your drawing and cut it around the areas on your drawing that you wanted zip-a-toned, and then peel off the parts you didn't want.
For this image, I just went with an alternating checkerboard pattern, with the lines two pixels wide. Because all the lines are drawn from one big (virtual) block of this checkerboard pattern, you never have to worry about weird artifacts at the joints or any overlap effects.
Angled lines are a bit tricky, but basically you imagine the edges of the line sort of cutting through pixels, and thus you draw them at the appropriate shade of grade instead of full black (in the case of the 45 degree line here, the pixels are drawn with RGB(170, 170, 170), but any angle could be rendered with appropriate shades).
I'm not sure if GDI+ could do this easily using the textured brushes, but maybe. Otherwise you'd have to custom-code it. The advantage of this method over just solid gray lines would be that this would allow some of the background to show through.
This is an interesting question that I never really thought about. I think the only real solution is to render the entire complex figure as a series of lines or paths that do not overlap anywhere. I'm not surprised that GDI+ doesn't handle this situation in any automatic way.