I'm writing an OSX app in Xcode using Objective-C. I have a window, with an NSView inside it, and that NSView is supposed to use data from an NSMutableArray containing NSNumbers to draw corresponding images on a grid such that images are drawn at 0,0; 32,0; 64,0 . . . 0,32; 32,32; etc. Accordingly the array's count is the grid's W*H, in this case 21*21 or 441.
You left click to "place" an image, which really just means updating the array based on where you clicked and then calling setNeedsDisplay:YES so it redraws itself to reflect the updated array. So far, I can get it to draw images based on the array properly.
When you right click, though, it is supposed to rotate the image in the particular grid slot by a certain amount. The only problem I am having here is figuring out how to actually draw the rotated images, in their proper locations. They should rotate about their center points, which would be the relative coordinates of 16,16 (all images are 32x32 pixels in size). As it is, my code is:
- (void)drawRect:(NSRect)dirtyRect
{
[super drawRect:dirtyRect];
//Black background
[[NSColor blackColor] setFill];
NSRectFill(dirtyRect);
// Drawing code here.
NSRect rectToDraw = CGRectMake(0,0,32,32);
NSInteger imageIndex = 0;
NSImage *imageToDraw = nil;
for (int i = 0; i < [objDataArray count]; i++) {
//Loop through data array and draw each image where it should be
if ([objDataArray objectAtIndex:i]==[NSNull null]) continue; //Don't draw anything in this slot
//Math to determine where to draw based on the current for loop index
//0 = 0,0; 1 = 32,0 . . . 20 = 640,0; 21 = 0,32; etc. (grid is 21x21)
rectToDraw.origin.x = (i % 21)*32;
rectToDraw.origin.y = floor(i/21)*32;
//Get the data at this index in the data array
imageIndex = [((NSNumber*)[objDataArray objectAtIndex:i]) integerValue];
//Use the retrieved number to get a corresponding image
imageToDraw = (NSImage*)[objImagesArray objectAtIndex:imageIndex];
//Draw that image at the proper location
[imageToDraw drawInRect:rectToDraw];
}
}
So say that the amount of rotation in degrees is specified by the variable rotationAmount. How do I change the drawInRect line (the last line before the closing braces) so that the image draws at the proper location specified by rectToDraw, but rotated by rotationAmount degrees about its center?
Thanks.
You don't draw the image rotated, as such. You transform the coordinate space and then draw the image.
[NSGraphicsContext saveGraphicsState];
NSAffineTransform* xform = [NSAffineTransform transform];
// Translate the image's center to the view origin so rotation occurs around it.
[xform translateXBy:-NSMidX(rectToDraw) yBy:-NSMidY(rectToDraw)];
[xform rotateByDegrees:rotationAmount];
[xform concat];
[imageToDraw drawInRect:NSOffsetRect(rectToDraw, -NSMidX(rectToDraw), -NSMidY(rectToDraw))];
[NSGraphicsContext restoreGraphicsState];
There's some chance that I have the transform backward. I always forget which way it goes (if it's transforming the view or the content). If your image goes off into never-never land, change the signs of the translation.
Related
This is a code snippet for creating a thumbnail sized image (from an original large image) and placing it appropriately on top of a tableviewcell. As i was studying the code i got stuck at the part where the thumbnail is being given a position by setting its abscissa and ordinate. In the method -(void)setThumbDataFromImage:(UIImage *)image they're setting the dimensions and coordinate for project thumbnail—
-(void)setThumbnailDataFromImage:(UIImage *)image{
CGSize origImageSize= [image size];
// the rectange of the thumbnail
CGRect newRect= CGRectMake(0, 0, 40, 40);
// figure out a scaling ratio to make sure we maintain the same aspect ratio
float ratio= MAX(newRect.size.width/origImageSize.width, newRect.size.height/origImageSize.height);
// Create a transparent bitmap context with a scaling factor equal to that of the screen
UIGraphicsBeginImageContextWithOptions(newRect.size, NO, 0.0);
// create a path that is a rounded rectangle
UIBezierPath *path= [UIBezierPath bezierPathWithRoundedRect:newRect cornerRadius:5.0];
// make all the subsequent drawing to clip to this rounded rectangle
[path addClip];
// center the image in the thumbnail rectangle
CGRect projectRect;
projectRect.size.width=ratio * origImageSize.width;
projectRect.size.height= ratio * origImageSize.height;
projectRect.origin.x= (newRect.size.width- projectRect.size.width)/2;
projectRect.origin.y= (newRect.size.height- projectRect.size.height)/2;
// draw the image on it
[image drawInRect:projectRect];
// get the image from the image context, keep it as our thumbnail
UIImage *smallImage= UIGraphicsGetImageFromCurrentImageContext();
[self setThumbnail:smallImage];
// get the PNG representation of the image and set it as our archivable data
NSData *data= UIImagePNGRepresentation(smallImage);
[self setThumbnailData:data];
// Cleanup image context resources, we're done
UIGraphicsEndImageContext();
}
I got the width and height computation wherein we multiply the origImageSize with scaling factor/ratio.
But then we use the following to give the thumbnail a position—
projectRect.origin.x= (newRect.size.width- projectRect.size.width)/2;
projectRect.origin.y= (newRect.size.height- projectRect.size.height)/2;
This i fail to understand. I cannot wrap my head around it. :?
Is this part of the centering process. I mean, are we using a mathematical relation here to position the thumbnail or is it some random calculation i.e could have been anything.. Am i missing some fundamental behind these two lines of code??
Those two lines are standard code for centering something, although they aren’t quite written in the most general way. You normally want to use:
projectRect.origin.x = newRect.origin.x + newRect.size.width / 2.0 - projectRect.size.width / 2.0;
projectRect.origin.y = newRect.origin.y + newRect.size.height / 2.0 - projectRect.size.height / 2.0;
In your case the author knows the origin is 0,0, so they omitted the first term in each line.
Since to center a rectangle in another rectangle you want the centers of the two axes to line up, you take, say, half the container’s width (the center of the outer rectangle) and subtract half the inner rectangle’s width (which takes you to the left side of the inner rectangle), and that gives you where the inner rectangle’s left side should be (e.g.: its x origin) when it is correctly centered.
- (void)drawRect:(CGRect)rect{
float sliceSize = rect.size.width / imagesShownAtOnce;
//Apply our clipping region and fill it with black
[clippingRegion addClip];
[clippingRegion fill];
//Draw the 3 images (+1 for inbetween), with our scroll amount.
CGPoint loc;
for (int i=0;i<imagesShownAtOnce+1;i++){
loc = CGPointMake(rect.origin.x+(i*sliceSize)-imageScroll, rect.origin.y);
[[buttonImages objectAtIndex:i] drawAtPoint:loc];
}
//Draw the text region background
[[UIColor blackColor] setFill];
[textRegion fillWithBlendMode:kCGBlendModeNormal alpha:0.4f];
//Draw the actual text.
CGRect textRectangle = CGRectMake(rect.origin.x+16,rect.origin.y+rect.size.height*4/5.6,rect.size.width/1.5,rect.size.height/3);
[[UIColor whiteColor] setFill];
[buttonText drawInRect:textRectangle withFont:[UIFont fontWithName:#"Avenir-HeavyOblique" size:22]];
}
clippingRegion and textRegion are UIBezierPaths to give me the rounded rectangles I want (First for a clipping region, 2nd as an overlay for my text)
The middle section is drawing 3 images and letting them scroll along, which im updating every 2 refreshes from a CADisplayLink, and that invalidates the draw region by calling [self setNeedsDisplay], and also increasing my imageScroll variable.
Now that that background information is done, here is my issue:
It runs, and even runs smoothly. But it is using up an absolutely high amount of CPU time (80%+)!! How do I push this off to the GPU on the phone instead? Someone told me about CALayers but I've never dealt with them before
Draw each component of your drawing once into something (a view or layer) and let it hold the cached the drawing. Then you just move or transform each component, and exactly as you say, it's all done by the GPU.
You could do this with individual views or with individual layers, but that doesn't really matter (a view is a layer, under the hood). The point is that there is no need to be constantly redrawing from scratch when all you really want is to move the same persistent pieces around.
Learning about CALayer would be a good idea, as it is in fact the basis of all drawing on iOS. What could be more important to know about than that?
I have an iPad application that has a base image UIImageView (in this case a large building or site plan or diagram) and then multiple 'pins' can be added on top of the plan (visually similar to Google Maps). These pins are also UIImageViews and are added to the main view on tap gestures. The base image is also added to the main view on viewDidLoad.
I have the base image working with the pinch gesture for zooming but obviously when you zoom the base image all the pins stay in the same x and y coordinates of the main view and loose there relative positioning on the base image (whose x,y and width,height coordinates have changed).
So far i have this...
- (IBAction)planZoom:(UIPinchGestureRecognizer *) recognizer;
{
recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
recognizer.scale = 1;
for (ZonePin *pin in planContainer.subviews) {
if ([pin isKindOfClass:[ZonePin class]]){
CGRect pinFrame = pin.frame;
// ****************************************
// code to reposition the pins goes here...
// ****************************************
pin.frame = pinFrame;
}
}
}
I need help to calculate the math to reposition the pins x/y coordinates to retain there relative position on the zoomed in or out plan/diagram. The pins obviously do not want to be scaled/zoomed at all in terms of their width or height - they just need new x and y coordinates that are relative to there initial positions on the plan.
I have tried to work out the math myself but have struggled to work it through and unfortunately am not yet acquainted with the SDK enough to know if there is provision available built in to help or not.
Help with this math related problem would be really appreciated! :)
Many thanks,
Michael.
InNeedOfMathTuition.com
First, you might try embedding your UIImageView in a UIScrollView so zooming is largely accomplished for you. You can then set the max and min scale easily, and you can scroll around the zoomed image as desired (especially if your pins are subviews of the UIImageView or something else inside the UIScrollView).
As for scaling the locations of the pins, I think it would work to store the original x and y coordinates of each pin (i.e. when the view first loads, when they are first positioned, at scale 1.0). Then when the view is zoomed, set x = (originalX * zoomScale) and y = (originalY * zoomScale).
I had the same problem in an iOS app a couple of years ago, and if I recall correctly, that's how I accomplished it.
EDIT: Below is more detail about how I accomplished this (I'm looking my old code now).
I had a UIScrollView as a subview of my main view, and my UIImageView as a subview of that. My buttons were added to the scroll view, and I kept their original locations (at zoom 1.0) stored for reference.
In -(void)scrollViewDidScroll:(UIScrollView *)scrollView method:
for (id element in myButtons)
{
UIButton *theButton = (UIButton *)element;
CGPoint originalPoint = //get original location however you want
[theButton setFrame:CGRectMake(
(originalPoint.x - theButton.frame.size.width / 2) * scrollView.zoomScale,
(originalPoint.y - theButton.frame.size.height / 2) * scrollView.zoomScale,
theButton.frame.size.width, theButton.frame.size.height)];
}
For the -(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView method, I returned my UIImageView. My buttons scaled in size, but I didn't include that in the code above. If you're finding that the pins are scaling in size automatically, you might have to store their original sizes as well as original coordinates and use that in the setFrame call.
UPDATE...
Thanks to 'Mr. Jefferson' help in his answer above, albeit with a differing implementation, I was able to work this one through as follows...
I have a scrollView which has a plan/diagram image as a subview. The scrollView is setup for zooming/panning etc, this includes adding UIScrollViewDelegate to the ViewController.
On user double tapping on the plan/diagram a pin image is added as a subview to the scrollView at the touch point. The pin image is a custom 'ZonePin' class which inherits from UIImageView and has a couple of additional properties including 'baseX' and 'baseY'.
The code for adding the pins...
- (IBAction)planDoubleTap:(UITapGestureRecognizer *) recognizer;
{
UIImage *image = [UIImage imageNamed:#"Pin.png"];
ZonePin *newPin = [[ZonePin alloc] initWithImage:image];
CGPoint touchPoint = [recognizer locationInView:planContainer];
CGFloat placementX = touchPoint.x - (image.size.width / 2);
CGFloat placementY = touchPoint.y - image.size.height;
newPin.frame = CGRectMake(placementX, placementY, image.size.width, image.size.height);
newPin.zoneRef = [NSString stringWithFormat:#"%#%d", #"BF", pinSeq++];
newPin.baseX = placementX;
newPin.baseY = placementY;
[planContainer addSubview:newPin];
}
I then have two functions for handling the scrollView interaction and this handles the scaling/repositioning of the pins relative to the plan image. These methods are as follows...
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return planImage;
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
for (ZonePin *pin in planContainer.subviews) {
if ([pin isKindOfClass:[ZonePin class]]){
CGFloat newX, newY;
newX = (pin.baseX * scrollView.zoomScale) + (((pin.frame.size.width * scrollView.zoomScale) - pin.frame.size.width) / 2);
newY = (pin.baseY * scrollView.zoomScale) + ((pin.frame.size.height * scrollView.zoomScale) - pin.frame.size.height);
CGRect pinFrame = pin.frame;
pinFrame.origin.x = newX;
pinFrame.origin.y = newY;
pin.frame = pinFrame;
}
}
}
For reference, the calculations for position the pins, by the nature of them being pins' centres the pin image on the x axis but has the y-axis bottom aligned.
The only thing left for me to do with this is to reverse the calculations used in the scrollViewDidScroll method when I add pins when zoomed in. The code for adding pins above will only work properly when the scrollView.zoomScale is 1.0.
Other than that, it now works great! :)
I have two instances of NSScrollView both presenting a view on the same content. The second scroll view however has a scaled down version of the document view presented in the first scroll view. Both width and height can be individually scaled and the original width - height constraints can be lost, but this is of no importance.
I have the synchronised scrolling working, even taking into account that the second scroll view needs to align its scrolling behaviour based on the scaling. There's one little snag I've been pulling my hairs out over:
As both views happily scroll along the smaller view needs to slowly catch up with the larger view, so that they both "arrive" at the end of their document at the same time. Right now this is not happening and the result is that the smaller view is at "end-of-document" before the larger view.
The code for synchronised scrolling is based on the example found in Apple's documentation titled "Synchronizing Scroll Views". I have adapted the synchronizedViewContentBoundsDidChange: to the following code:
- (void) synchronizedViewContentBoundsDidChange: (NSNotification *) notification {
// get the changed content view from the notification
NSClipView *changedContentView = [notification object];
// get the origin of the NSClipView of the scroll view that
// we're watching
NSPoint changedBoundsOrigin = [changedContentView documentVisibleRect].origin;;
// get our current origin
NSPoint curOffset = [[self contentView] bounds].origin;
NSPoint newOffset = curOffset;
// scrolling is synchronized in the horizontal plane
// so only modify the x component of the offset
// "scale" variable will correct for difference in size between views
NSSize ownSize = [[self documentView] frame].size;
NSSize otherSize = [[[self synchronizedScrollView] documentView] frame].size;
float scale = otherSize.width / ownSize.width;
newOffset.x = floor(changedBoundsOrigin.x / scale);
// if our synced position is different from our current
// position, reposition our content view
if (!NSEqualPoints(curOffset, changedBoundsOrigin)) {
// note that a scroll view watching this one will
// get notified here
[[self contentView] scrollToPoint:newOffset];
// we have to tell the NSScrollView to update its
// scrollers
[self reflectScrolledClipView:[self contentView]];
}
}
How would I need to change that code so that the required effect (both scroll bars arriving at an end of document) is achieved?
EDIT: Some clarification as it was confusing when I read it back myself: The smaller view needs to slow down when scrolling the first view reaches the end. This would probably mean re-evaluating that scaling factor... but how?
EDIT 2: I changed the method based on Alex's suggestion:
NSScroller *myScroll = [self horizontalScroller];
NSScroller *otherScroll = [[self synchronizedScrollView] horizontalScroller];
//[otherScroll setFloatValue: [myScroll floatValue]];
NSLog(#"My scroller value: %f", [myScroll floatValue]);
NSLog(#"Other scroller value: %f", [otherScroll floatValue]);
// Get the changed content view from the notification.
NSClipView *changedContentView = [notification object];
// Get the origin of the NSClipView of the scroll view that we're watching.
NSPoint changedBoundsOrigin = [changedContentView documentVisibleRect].origin;;
// Get our current origin.
NSPoint curOffset = [[self contentView] bounds].origin;
NSPoint newOffset = curOffset;
// Scrolling is synchronized in the horizontal plane so only modify the x component of the offset.
NSSize ownSize = [[self documentView] frame].size;
newOffset.x = floor(ownSize.width * [otherScroll floatValue]);
// If our synced position is different from our current position, reposition our content view.
if (!NSEqualPoints(curOffset, changedBoundsOrigin)) {
// Note that a scroll view watching this one will get notified here.
[[self contentView] scrollToPoint: newOffset];
// We have to tell the NSScrollView to update its scrollers.
[self reflectScrolledClipView:[self contentView]];
}
Using this method the smaller view is "overtaken" by the larger view when both scrollers reach a value of 0.7, which is not good. The larger view then scrolls past its end of document.
I think you might be approaching this in the wrong way. I think you should be getting a percentage of how far down each scroll be is scrolled in relation to itself and apply that to the other view. One example of how this could be done is this way using NSScroller's -floatValue:
NSScroller *myScroll = [self verticalScroller];
NSScroller *otherScroll = [otherScrollView verticalScroller];
[myScroll setFloatValue:otherScroll.floatValue];
I finally figured it out. The answer from Alex was a good hint but not the full solution as just setting the float value of a scroller doesn't do anything. That value needs translation to specific coordinates to which the scroll view needs to scroll its contents.
However, due to differences in size of the scrolled document view, you cannot just simply use this value, as the scaled down view will be overtaken by the "normal" view at some point. This will cause the normal view to scroll past its end of document.
The second part of the solution was to make the normal sized view wait with scrolling until the scaled down view has scrolled its own width.
The code:
// Scrolling is synchronized in the horizontal plane so only modify the x component of the offset.
NSSize ownSize = [[self documentView] frame].size;
newOffset.x = MAX(floor(ownSize.width * [otherScroll floatValue] - [self frame].size.width),0);
The waiting is achieved by subtracting the width of the scroll view from the width times the value of the scroller. When the scaled down version is still traversing its first scroll view width of pixels, this calculation will result in a negative offset. Using MAX will prevent strange effects and the original view will quietly wait until the value turns positive and then start its own scrolling. This solution also works when the user resizes the app window.
I have an NSTableView in my application with data being drawn in for both the X and Y axes (ie, every row is matched with every column.) I've got the data populating the cells the way I'd like, but it looks terrible with the columns stretched out horizontally.
I would like to turn the NSTextFieldCell on its side, so that the text is written vertically instead of horizontally. I realize that I'm probably going to have to subclass the NSTextFieldCell, but I'm not sure which functions I'm going to need to override in order to accomplish what I want to do.
What functions in NSTextFieldCell draw the text itself? Is there any built-in way to draw text vertically instead of horizontally?
Well, it took a lot of digging to figure this one out, but I eventually came across the NSAffineTransform object, which apparently can be used to shift the entire coordinate system with respect to the application. Once I had figured that out, I subclassed NSTextViewCell and overrode the -drawInteriorWithFrame:inView: function to rotate the coordinate system around before drawing the text.
- (void)drawInteriorWithFrame:(NSRect)cellFrame inView:(NSView *)controlView {
// Save the current graphics state so we can return to it later
NSGraphicsContext *context = [NSGraphicsContext currentContext];
[context saveGraphicsState];
// Create an object that will allow us to shift the origin to the center
NSSize originShift = NSMakeSize(cellFrame.origin.x + cellFrame.size.width / 2.0,
cellFrame.origin.y + cellFrame.size.height / 2.0);
// Rotate the coordinate system
NSAffineTransform* transform = [NSAffineTransform transform];
[transform translateXBy: originShift.width yBy: originShift.height]; // Move origin to center of cell
[transform rotateByDegrees:270]; // Rotate 90 deg CCW
[transform translateXBy: -originShift.width yBy: -originShift.height]; // Move origin back
[transform concat]; // Set the changes to the current NSGraphicsContext
// Create a new frame that matches the cell's position & size in the new coordinate system
NSRect newFrame = NSMakeRect(cellFrame.origin.x-(cellFrame.size.height-cellFrame.size.width)/2,
cellFrame.origin.y+(cellFrame.size.height-cellFrame.size.width)/2,
cellFrame.size.height, cellFrame.size.width);
// Draw the text just like we normally would, but in the new coordinate system
[super drawInteriorWithFrame:newFrame inView:controlView];
// Restore the original coordinate system so that other cells can draw properly
[context restoreGraphicsState];
}
I now have an NSTextCell that draws its contents sideways! By changing the row height, I can give it enough room to look good.