I have painting app witch works like that:
On mouseDown/mouseDragged event I draw a point in event location with
CIRadialGradient
Take CIRadialGradient outputImage and use it in CISourceOverCompositing
filter as inputImage (inputBackground at beggining is empty CIImage)
Set CISourceOverCompositing outputImage as brushAccumulator image
(later brushAccumulator image is used as inputBackgroundImage in
CISourceOverCompositing filter)
Set brushAccumulator image as CIBlendWithMask inputMaskImage Set
CIBlendWithMask outputImage as mainImageAccumulator image Draw
mainImageAccumulator to screen
And I want to implement undo method. Firstly I thought I could use brushAccumulator.image (CIImage) as undo object (add it to mutableArray, then when undo method is invoked set brushAccumulator image to one of mutableArray objects) but I found that:
A CIImage is not an image that contains pixels, it is simply the result of a series of instructions to build it, the output of a CIFilter for example. So if you copy the CIImage you just copy those instructions, which when modified would modify the ouput.
So I thought I could make NSBitmapImageRep from brushAccumulator's image and store it to NSMutableArray. But I met problems with updating brushAccumulator. I set the new CIImage wich is made from one of NSBitmapImageRep from NSMutableArray as brushAccumulator image, but brushAccumulator image doesn't changes.
What could you offer me to achieve undo/redo effect, while my painting app is based on CIImageAccumulator (similar to CIMicroPaint sample code)?
Here's a general algorithm that works for me. You'll need to copies of your image:
1) The one you are drawing directly to- "direct bitmap"
2) A copy of what it looks like before the draw operation- "undo bitmap"
So you draw to the direct, and take note of what the change frame is ("changeFrame")
Then you copy out the changeFrame from the undo context to be used later on for an undo (and store the changeFrame along with it in some object- SOChangeBitmap).
Then you pull an image from changeFrame of the direct bitmap, and replace the pixels in the undo bitmap w/ the change frame.
Then, to undo, you take the SOChangeBitmap (image + changeFrame) and apply it to the direct bitmap (and update the undo bitmap as well).
Related
I have a UITableView with custom cells. I need to display Title, Address, Zip, Phone, Email, Website and Description in a Cell. All this information is coming from webserver. I am able to display the contents from the webserver. However, if any of the content is empty, there is a gap where that content should be, and if description is too long I am not able to display all the content. How can I change the height of cell according to the content from server? Please help.
For example : the contents is printing like:
Title
Address
Zip
Phone...
but, if Address is nil then it looks like:
Title
Zip
Phone...
I have the tableview:heightForRowAtIndexPath method but I am not able to update the cell height according to the cell contents.
Sorry for bad question format
Cells resizing can get pretty complicated, so I suggest you simply use a table view framework such as "Sensible TableView", where all the cells are automatically resized to fit contents. I believe they also now have a free version.
you can set the height of every cell with this delegate method
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *text = [yourArray objectAtIndex:indexPath.row];// here just use your data array which you get from server
CGSize mTempSize = [text sizeWithFont:[UIFont fontWithName:fontName size:fontSize] constrainedToSize:constrainedToSize lineBreakMode:UILineBreakModeWordWrap];
return mTempSize.height ;
}
i hope this help you...
Firstly you need to set the size of your labels according to it's text length. There are a number of sizeWithFont methods available to get size for a string. See Apple Developer Documentation
If you have single line labels you can use simplest of them – sizeWithFont:. But if you have multiline labels you should use – sizeWithFont:constrainedToSize:. This method lets you specify the maximum size you want the label be.
Secondly you have to return calculated height for your cell using tableView:heightForRowAtIndexPath:
Hope this helps you.
Your tableView:heightForRowAtIndexPath: call will need to tabe into account the missing data and how all the rest of the cell will be re-laid out to close the gap it leaves. So, your actual call will be non-trivial here.
The new facebook app does a neat trick here, though, to save you calling it every time. It calculates all of the cell heights in the background, just after downloading it, and before rendering the content to the user, storing it in the data store alongside the data itself. This means that the actual table cell rendering is really fast and slick as you don't need to re-layout/recalculate the cell height and layout on each app run/cell reuse.
I have a small question, I have a code to generate 200 UIImages in random positions and rotations.
I need to detect the touch event on these images, but I need to check if the touched UIImage is not covered by any other image (even if they intersect in a small area).
Can anybody help me on this?
BTW : I'm trying to do something similar to this game : http://www.dressup247.com/game/1014/Bank-Note-Stack.html
I would suggest to make all images as UIButton's with background image and set for all buttons one action. One more advise - set tag order for every button from most low-lying to most high-lying (and store biggest tag in some iVar). You can do it when layout is generated. It allows you to detect how many views lay over tapped view.
Use CGRectIntersectsRect intersecting views.
-(IBAction)banknotTapped:(UIButton*)sender{
int tag = sender.tag
NSMutableArray *highestViews = [NSMutableArray array];
for (int i=sender.tag; i < biggestTag; ++i){
UIView *v = [self.view viewWithTag:i];
if (CGRectIntersectsRect(sender.frame, v.frame) ) // it allows to find intersecting views
[highestViews addObject:v];
}
}
Now highestViews will contain all highest views that intersect with sender.
Note: tags allow you to detect views, but if you will delete images from superview then it can lead to problems since tag order will broken. Hide views instead of deleting or follow #Costique method in order to determine views order.
You can use the following snippet to determine the order of a subview in its parent view:
NSUInteger order = [containerView.subviews indexOfObjectIdenticalTo: subview];
The less the order, the "higher" the subview is. The topmost subview will have zero order.
While I'd suggest that it would be faster to do this mathematically, defining the banknotes as rectangles and testing for overlap using something like the separating axes theorem, that's obviously not what you're asking and not suitable for general case images.
So I'd suggest that you create a CGBitmapContext the same size as your play area and that when seeding your play area, for each note you place you do something like:
assign new, as yet unused colour to the bank note
draw it to the bitmap context at its destination position, but as a solid object of the assigned colour — so you preserve the outline of the original shape but at each pixel you draw either the solid, assigned colour or no colour at all
count how many pixels in the entire context are now the assigned colour, store that with your object representing the note
Subsequently, when the game starts run through the buffer and count how many of each assigned colour. All notes that have the same number stored as are currently visible are on top. Whenever a note is removed, redraw all the others in order and do the colour count once.
Note that you're not doing the colour count on the total buffer once per note, just once in total. So it's a fixed cost and probably occurs less often than once per tap.
Probably the easiest way to do the drawing as a single colour is to create a mask version of each graphic when it's loaded and then to draw that with a suitable tint. There's an introduction to alpha masks here; you'll probably want to create a custom bitmap image context rather than using the implicit one returned by UIGraphicsGetCurrentContext and to post filter to test the output alpha — pushing down to 0 if its less than some threshold, up to 255 otherwise.
I have an NSImageCell table column whose valuePath is bound to a path supplied by my object through an NSArrayController.
My NSTableViewDelegate implements the -tableView:heightOfRow: method, in order to have variable row height. I need to calculate row height based on the dimensions of the image displayed in the aforementioned column.
Right now, I'm getting horrible performance, though, since I'm calling [[NSImage alloc] initWithContentsOfFile:<path>] for each iteration. Is there any way to load the image representation that each NSImageCell has already retrieved for display?
I'm happy with the performance exhibited by using the valuePath binding, and would rather not cache each image on my own, as there will be many of them, each somewhat large.
I tried the NSTableColumn method -dataCellForRow:, which sounded perfect, except the cell returned returns an objectValue that seems to be the last row for which data was loaded.
Update (solution, unsatisfactory)
I figured out an approximate solution (posted simultaneously below), but it seems clumsy (and I've already seen it fail at random, irreproducible times), and I am still looking for a better solution.
I'm using the -tableView:willDisplayCell:forTableColumn:row: delegate method to populate a mutable dictionary with [[cell objectValue] size] (the image's size) keyed to the represented object's unique ID. Then, in the -tableView:heightOfRow: call I'm looking up the cover from this dictionary. I need to call [tableView noteNumberOfRowsChanged] after data is loaded, otherwise the dictionary isn't filled properly for the initial screen of data.
I tried the NSTableColumn method -dataCellForRow:, which sounded perfect, except the cell returned returns an objectValue that seems to be the last row for which data was loaded.
That's because the NSTableColumn only uses a single data cell for displaying the entire column, swapping out its value as it draws.
If I were you, I would probably try implementing the – tableView:willDisplayCell:forTableColumn:row: method in your NSTableViewDelegate. Then you can intercept the cell before it's about to be drawn, get its value at that moment, and cache just its height (as an NSNumber* or CGFloat). Then you can return that value in -tableView:heightOfRow:.
Then again, it's possible that -tableView:heightOfRow: gets called before – tableView:willDisplayCell:forTableColumn:row:, so that might not work. I'm not sure. But that's where I would start.
how to generate an end screen when two images collide. I am making an app with a stickman you move with a very sensitive acceremeter. SO if it hits these spikes, (UIImages) it will generate the end screen. How do I make the app detect this collision and then generate an end screen.
I'm sure you know the rect of the two images because you need to draw them so you can use
bool CGRectIntersectsRect (
CGRect rect1,
CGRect rect2
);
It returns YES if the two rects have a shared point
The fact that you haven't declared any rects doesn't matter. You need rects for collision detection. I assume that you at least have x and y coordinates for the stickman and you should have some kind of idea of his height and width. Judging from the question title it seems like you're using images to draw the objects you want to check for collision, so you should know the height and width of the images you're using. If you don't have this info you can't draw the objects in the right place and you certainly can't check for collisions.
You basically want to use the same rects that you use for drawing the objects.
Some code examples:
If your coordinates point to the middle of the stickman you would use something like the following:
if (CGRectIntersectsRect(CGRectMake(stickman.x-stickman.width/2,
stickman.y-stickman.height/2,
stickman.width,
stickman.height),
CGRectMake(spikes.x-spikes.width/2,
spikes.y-spikes.height/2,
spikes.width,
spikes.height))) {
// Do whatever it is you need to do. For instance:
[self showEndScreen];
}
If your coordinates point to the top left corner of your stickman you would use:
if (CGRectIntersectsRect(CGRectMake(stickman.x,
stickman.y,
stickman.width,
stickman.height),
CGRectMake(spikes.x,
spikes.y,
spikes.width,
spikes.height))) {
// Do whatever it is you need to do. For instance:
[self showEndScreen];
}
If I might give you a suggestion, I would suggest storing the coordinates and sizes in a CGRect, so that you don't have to create a new CGRect every time you're checking for collision.
in a simple drawing application I have a model which has a NSMutableArray curvedPaths holding all the lines the user has drawn. A line itself is also a NSMutableArray, containing the point objects. As I draw curved NSBezier paths, my point array has the following structure: linePoint, controlPoint, controlPoint, linePoint, controlPoint, controlPoint, etc... I thought having one array holding all the points plus control points would be more efficient than dealing with 2 or 3 different arrays.
Obviously my view draws the paths it gets from the model, which leads to the actual question: Is there a way to optimize the following code (inside the view's drawRect method) in terms of speed?
int lineCount = [[model curvedPaths] count];
// Go through paths
for (int i=0; i < lineCount; i++)
{
// Get the Color
NSColor *theColor = [model getColorOfPath:[[model curvedPaths] objectAtIndex:i]];
// Get the points
NSArray *thePoints = [model getPointsOfPath:[[model curvedPaths] objectAtIndex:i]];
// Create a new path for performance reasons
NSBezierPath *path = [[NSBezierPath alloc] init];
// Set the color
[theColor set];
// Move to first point without drawing
[path moveToPoint:[[thePoints objectAtIndex:0] myNSPoint]];
int pointCount = [thePoints count] - 3;
// Go through points
for (int j=0; j < pointCount; j+=3)
{
[path curveToPoint:[[thePoints objectAtIndex:j+3] myNSPoint]
controlPoint1:[[thePoints objectAtIndex:j+1] myNSPoint]
controlPoint2:[[thePoints objectAtIndex:j+2] myNSPoint]];
}
// Draw the path
[path stroke];
// Bye stuff
[path release];
[theColor release];
}
Thanks,
xonic
Hey xon1c, the code looks good. In general it is impossible to optimize without measuring performance in specific cases.
For example, lets say the code above is only ever called once. It draws a picture in a view and it never needs redrawing. Say the code above takes 50 milliseconds to run. You could rewrite it in openGL and do every optimisation under the sun and get that time down to 20 milliseconds and realistically the 30 milliseconds that you have saved makes no difference to anyone and you pretty much just wasted your time and added a load of code-bloat that is going to be more difficult to maintain.
However, if the code above is called 50 times a second and most of those times it is drawing the same thing then you could meaningfully optimise it.
When it comes to drawing the best way to optimise is to is to eliminate unnecessary drawing.
Each time you draw you recreate the NSBezierPaths - are they always different? You may want to maintain the list of NSBezier paths to draw, keep that in sync with your model, and keep drawrect solely for drawing the paths.
Are you drawing to areas of your view which don't need redrawing? The argument to drawrect is the area of the view that needs redrawing - you could test against that (or getRectsBeingDrawn:count:), but it may be in your case that you know that the entire view needs to be redrawn.
If the paths themselves don't change often, but the view needs redrawing often - eg when the shapes of the paths aren't changing but their positions are animating and they overlap in different ways, you could draw the paths to images (textures) and then inside drawrect you would draw the texture to the view instead of drawing the path to the view. This can be faster because the texture is only created once and uploaded to video memory which is faster to draw to the screen. You should look at Core Animation if this is what you need todo.
If you find that drawing the paths is too slow you could look at CGPath
So, on the whole, it really does depend on what you are doing. The best advice is, as ever, not to get sucked into premature optimisation. If your app isn't actually too slow for your users, your code is just fine.