drawing interview questions
Top drawing frequently asked interview questions
How can i convert an array of bitmaps into a brand new image of TIFF format, adding all the bitmaps as frames in this new tiff image?
using .NET 2.0.
Source: (StackOverflow)
I am trying to create a drawing area with canvas. I am having trouble with making the lines look smooth when drawing curves and I also have changing line thickness in my algorithm which looks bad as well because the size jumps to much as well and you can see where the size changed. I did find this link on stackoverflow but this was for a native iPhone app and I can't figure it out.
Here is my current JS code. and Here is it running on jsFiddle
var xStart,
xEnd,
yStart,
yEnd,
paint,
ctx;
$(document).ready(function (){
ctx = $('canvas')[0].getContext("2d");
ctx.strokeStyle = '#000';
ctx.lineJoin="round";
ctx.lineCap="round";
ctx.lineWidth = 1;
$('canvas').bind('mousedown mousemove mouseup mouseleave touchstart touchmove touchend', function(e){
var orig = e.originalEvent;
if(e.type == 'mousedown'){
e.preventDefault(); e.stopPropagation();
xStart = e.clientX - $(this).offset().left;
yStart = e.clientY - $(this).offset().top;
xEnd = xStart;
yEnd = yStart;
paint = true;
draw(e.type);
}else if(e.type == 'mousemove'){
if(paint==true){
xEnd = e.clientX - $(this).offset().left;
yEnd = e.clientY - $(this).offset().top;
lineThickness = 1 + Math.sqrt((xStart - xEnd) *(xStart-xEnd) + (yStart - yEnd) * (yStart-yEnd))/5;
if(lineThickness > 10){
lineThickness = 10;
}
ctx.lineWidth = lineThickness;
draw(e.type);
}
}else if(e.type == 'mouseup'){
paint = false;
}else if(e.type == 'mouseleave'){
paint = false;
}else if(e.type == 'touchstart'){
if(orig.touches.length == 1){
e.preventDefault(); e.stopPropagation();
xStart = orig.changedTouches[0].pageX - $(this).offset().left;
yStart = orig.changedTouches[0].pageY - $(this).offset().top;
xEnd = xStart;
yEnd = yStart;
paint = true;
draw(e.type);
}
}else if(e.type == 'touchmove'){
if(orig.touches.length == 1){
if(paint==true){
xEnd = orig.changedTouches[0].pageX - $(this).offset().left;
yEnd = orig.changedTouches[0].pageY - $(this).offset().top;
lineThickness = 1 + Math.sqrt((xStart - xEnd) *(xStart-xEnd) + (yStart - yEnd) * (yStart-yEnd))/6;
if(lineThickness > 10){
lineThickness = 10;
}
ctx.lineWidth = lineThickness;
draw(e.type);
}
}
}else if(e.type == 'touchend'){
paint = false;
}
});
});
function draw(event){
if(event == 'mousedown'){
ctx.beginPath();
ctx.moveTo(xStart, yStart);
ctx.lineTo(xEnd, yEnd);
ctx.stroke();
}else if(event == 'mousemove'){
ctx.beginPath();
ctx.moveTo(xStart, yStart);
ctx.lineTo(xEnd, yEnd);
ctx.stroke();
}else if(event == 'touchstart'){
ctx.beginPath();
ctx.moveTo(xStart, yStart);
ctx.lineTo(xEnd, yEnd);
ctx.stroke();
}else if(event == 'touchmove'){
ctx.beginPath();
ctx.moveTo(xStart, yStart);
ctx.lineTo(xEnd, yEnd);
ctx.stroke();
}
xStart = xEnd;
yStart = yEnd;
}
Thank you all in advance.
This is what it looks like right now if you draw. 
... and this is what I would love to achieve:
Source: (StackOverflow)
In my office at work, we are not allowed to paint the walls, so I have decided to frame out squares and rectangles, attach some nice fabric to them, and arrange them on the wall.
I am trying to write a method which will take my input dimensions (9' x 8' 8") and min/max size (1' x 3', 2', 4', etc..) and generate a random pattern of squares and rectangles to fill the wall. I tried doing this by hand, but I'm just not happy with the layout that I got, and it takes about 35 minutes each time I want to 'randomize' the layout.
Source: (StackOverflow)
The following SVG path can draw 99.99% of a circle: (try it on http://jsfiddle.net/DFhUF/46/ and see if you see 4 arcs or only 2, but note that if it is IE, it is rendered in VML, not SVG, but have the similar issue)
M 100 100 a 50 50 0 1 0 0.00001 0
But when it is 99.99999999% of a circle, then nothing will show at all?
M 100 800 a 50 50 0 1 0 0.00000001 0
And that's the same with 100% of a circle (it is still an arc, isn't it, just a very complete arc)
M 100 800 a 50 50 0 1 0 0 0
How can that be fixed? The reason is I use a function to draw a percentage of an arc, and if I need to "special case" a 99.9999% or 100% arc to use the circle function, that'd be kind of silly.
Again, a test case on jsfiddle using RaphaelJS is at http://jsfiddle.net/DFhUF/46/
(and if it is VML on IE 8, even the second circle won't show... you have to change it to 0.01)
Update:
This is because I am rendering an arc for a score in our system, so 3.3 points get 1/3 of a circle. 0.5 gets half a circle, and 9.9 points get 99% of a circle. But what if there are scores that are 9.99 in our system? Do I have to check whether it is close to 99.999% of a circle, and use an arc function or a circle function accordingly? Then what about a score of 9.9987? Which one to use? It is ridiculous to need to know what kind of scores will map to a "too complete circle" and switch to a circle function, and when it is "a certain 99.9%" of a circle or a 9.9987 score, then use the arc function.
Source: (StackOverflow)
I'd like to create an empty bitmap and set canvas to that bitmap and then draw any shape on bitmap.
Source: (StackOverflow)
I was playing around with drawing paths, and I noticed that in at least some cases, UIBezierPath outperforms what I thought would be a Core Graphics equivalent. The -drawRect: method below creates two paths: one UIBezierPath, and one CGPath. The paths are identical except for their locations, but stroking the CGPath takes roughly twice as long as stroking the UIBezierPath.
- (void)drawRect:(CGRect)rect
{
CGContextRef ctx = UIGraphicsGetCurrentContext();
// Create the two paths, cgpath and uipath.
CGMutablePathRef cgpath = CGPathCreateMutable();
CGPathMoveToPoint(cgpath, NULL, 0, 100);
UIBezierPath *uipath = [[UIBezierPath alloc] init];
[uipath moveToPoint:CGPointMake(0, 200)];
// Add 200 curve segments to each path.
int iterations = 200;
CGFloat cgBaseline = 100;
CGFloat uiBaseline = 200;
CGFloat xincrement = self.bounds.size.width / iterations;
for (CGFloat x1 = 0, x2 = xincrement;
x2 < self.bounds.size.width;
x1 = x2, x2 += xincrement)
{
CGPathAddCurveToPoint(cgpath, NULL, x1, cgBaseline-50, x2, cgBaseline+50, x2, cgBaseline);
[uipath addCurveToPoint:CGPointMake(x2, uiBaseline)
controlPoint1:CGPointMake(x1, uiBaseline-50)
controlPoint2:CGPointMake(x2, uiBaseline+50)];
}
[[UIColor blackColor] setStroke];
CGContextAddPath(ctx, cgpath);
// Stroke each path.
[self strokeContext:ctx];
[self strokeUIBezierPath:uipath];
[uipath release];
CGPathRelease(cgpath);
}
- (void)strokeContext:(CGContextRef)context
{
CGContextStrokePath(context);
}
- (void)strokeUIBezierPath:(UIBezierPath*)path
{
[path stroke];
}
Both paths use CGContextStrokePath(), so I created separate methods to stroke each path so that I can see the time used by each path in Instruments. Below are typical results (call tree inverted); you can see that -strokeContext: takes 9.5 sec., while -strokeUIBezierPath: takes only 5 sec.:
Running (Self) Symbol Name
14638.0ms 88.2% CGContextStrokePath
9587.0ms 57.8% -[QuartzTestView strokeContext:]
5051.0ms 30.4% -[UIBezierPath stroke]
5051.0ms 30.4% -[QuartzTestView strokeUIBezierPath:]
It looks like UIBezierPath is somehow optimizing the path that it creates, or I'm creating the CGPath in a naïve way. What can I do to speed up my CGPath drawing?
Source: (StackOverflow)
Is it possible to draw unfilled figures on Android? By default circles and rectangles are filled.
Source: (StackOverflow)
I have an interesting question.
Imagine I have a lot of data changing in very fast intervals.
I want to display that data as a table in console app. f.ex:
-------------------------------------------------------------------------
| Column 1 | Column 2 | Column 3 | Column 4 |
-------------------------------------------------------------------------
| | | | |
| | | | |
| | | | |
-------------------------------------------------------------------------
How to keep things fast and how to fix column widths ? I know how to do that in java, but I don't how it's done in C#.
Source: (StackOverflow)
I'm trying to work on a project where I can animate the windows 7 wallpaper, either with opengl/directx, or GDI. I looked into how the windows desktop windows are laid out, and i figured out the whole
"Progman" -> "SHELLDLL_DefView" -> "SysListView32"
hierarchy.
I tried hooking the SysListView32's WndProc and tried messing around with the messages using an injected c# dll so I could prevent the desktop from drawing the wallpaper when I forced it to change using the Control Panel -> Personalize menu. None of this actually stopped the wallpaper from being updated, so I figured that explorer.exe does not actually handle drawing the wallpaper.
To confirm this, I killed explorer.exe and set up a little c# program that changes the wallpaper on a 10 second timer to a random one. As I expected, the wallpaper kept changing, leading me to believe that explorer.exe does not actually handle the drawing of the wallpaper!
Unfortunately, this is where i'm completely lost. I have no idea what else is responsible for drawing the wallpaper, and how I can take over it's drawing so I can handle the drawing. I've tried to google this for a few days now, with little progress. I'm hoping someone here can guide me in the right direction.
Source: (StackOverflow)
I am creating different custom views with two different colors. According to my app features user will drag those objects on the screen, when dragging objects will overlap each other. I want to differentiated the overlapped area, how to set the combined color for overlapped Area.
Look at the below image. Here I am using canvas for creating those custom views two circles are two different views.
EDIT: If I use opacity 128 I am able to see the background color, but I want the combination color of overlapped objects colors.
Source: (StackOverflow)
I'm trying to stretch a navigation arrow image while preserving the edges so that the middle stretches and the ends are fixed.
Here is the image that I'm trying to stretch:
The following iOS 5 code allows the image when resized to stretch the center portions of the image defined by the UIEdgeInsets.
[[UIImage imageNamed:@"arrow.png"] resizableImageWithCapInsets:UIEdgeInsetsMake(15, 7, 15, 15)];
This results in an image that looks like this (if the image's frame is set to 70 pixels wide):
This is actually what I want but resizableImageWithCapInsets is only supported on iOS 5 and later.
Prior to iOS 5 the only similar method is stretchableImageWithLeftCapWidth:topCapHeight but you can only specify the top and left insets which means the image has to have equal shaped edges.
Is there an iOS 4 way of resizing the image the same as iOS 5's resizableImageWithCapInsets method, or another way of doing this?
Source: (StackOverflow)
I have two questions actually:
- Is it better to draw an image on a bitmap or create a bitmap as resource and then draw it over a bitmap? Performance wise... which one is better?
- If I want to draw something transparent over a bitmap, how would I go about doing it?
- If I want to overlay one transparent bitmap over another, how would I do it?
Sorry for the long list, but in the interest of learning, I would like to explore both the approaches...
Source: (StackOverflow)
Can anyone guide how to generate image from input text. Image might have any extension doesn't matter.
Source: (StackOverflow)
I want to load and draw pdf files graphically using C#. I don't need to edit them or anything, just render them at a given zoom level.
The pdf libraries I have found seem to be focussed on generation. How do I do this?
Thanks.
Source: (StackOverflow)