I want to draw some text in a view, rotated 90°. I'm pretty new to iPhone development, and poking around the web reveals a number of different solutions. I've tried a few and usually end up with my text getting clipped.
What's going on here? I am drawing in a fairly small space (a table view cell), but there has to be a "right" way to do this… right?
Edit: Here are a couple of examples. I'm trying to display the text "12345" along the black bar at the left.
First attempt, from RJShearman on the Apple Discussions
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSelectFont (context, "Helvetica-Bold", 16.0, kCGEncodingMacRoman);
CGContextSetTextDrawingMode (context, kCGTextFill);
CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextSetTextMatrix (context, CGAffineTransformRotate(CGAffineTransformScale(CGAffineTransformIdentity, 1.f, -1.f ), M_PI/2));
CGContextShowTextAtPoint (context, 21.0, 55.0, [_cell.number cStringUsingEncoding:NSUTF8StringEncoding], [_cell.number length]);
CGContextRestoreGState(context);
(source: deeptechinc.com)
Second attempt, from zgombosi on iPhone Dev SDK. Identical results (the font was slightly smaller here, so there's less clipping).
CGContextRef context = UIGraphicsGetCurrentContext();
CGPoint point = CGPointMake(6.0, 50.0);
CGContextSaveGState(context);
CGContextTranslateCTM(context, point.x, point.y);
CGAffineTransform textTransform = CGAffineTransformMakeRotation(-1.57);
CGContextConcatCTM(context, textTransform);
CGContextTranslateCTM(context, -point.x, -point.y);
[[UIColor redColor] set];
[_cell.number drawAtPoint:point withFont:[UIFont fontWithName:#"Helvetica-Bold" size:14.0]];
CGContextRestoreGState(context);
Attempt two. There is almost identical clipping http://dev.deeptechinc.com/sidney/share/iphonerotation/attempt2.png
It turns out that the my table cell was always initialized 44px high regardless of the row height, so all of my drawing was getting clipped 44px from the top of the cell.
To draw larger cells it was necessary to set the content view's autoresizingMask with
cellContentView.autoresizingMask = UIViewAutoresizingFlexibleHeight;
or
cellContentView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
…and drawRect is called with the correct size. In a way, this makes sense, because UITableViewCell's initWithStyle:reuseIdentifier: makes no mention of the size of the cell, and only the table view actually knows how big each row is going to be, based on its own size and its delegate's response to tableView:heightForRowAtIndexPath:.
I read the Quartz 2D Programming Guide until the drawing model and functions started to make sense, and the code to draw my rotated text became simple and obvious:
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextRotateCTM(context, -(M_PI/2));
[_cell.number drawAtPoint:CGPointMake(-57.0, 5.5) withFont:[UIFont fontWithName:#"Helvetica-Bold" size:16.0]];
CGContextRestoreGState(context);
Thanks for the tips, it looks like I'm all set.
Use :-
label.transform = CGAffineTransformMakeRotation(- 90.0f * M_PI / 180.0f);
where label is the object of UILabel.
Here's a tip. I presume you're doing this drawing in drawRect. Why don't you draw a frame around drawRect to see how big the rect is and if that is why you get clipping.
An alternative is to put your text in a UILabel, and then rotate that 90 degrees when you make your cells in cellForRowAtIndexPath.
You know about the UITableViewDelegate method heightForRowAtIndexPath right?
Here's a simple tutorial on various graphics level methods. Presuming you know how big your text is you should be able to size your table view row size appropriately.
Also, I'd check to make sure that the bounds after any transform actually meet your expectations. (Either use a debugger or log statement to verify this).
to what #Sidnicious said, and what i collected through out stack overflow, i want to give a usage example - appended my code to completely draw a ruler to the left screen side, with numbers rotated:
RulerView : UIView
// simple testing for iPhones (check for device descriptions to get all iPhones + iPads)
- (float)getPPI
{
switch ((int)[UIScreen mainScreen].bounds.size.height) {
case 568: // iPhone 5*
case 667: // iPhone 6
return 163.0;
break;
case 736: // iPhone 6+
return 154.0;
break;
default:
return -1.0;
break;
}
}
- (void)drawRect:(CGRect)rect
{
[[UIColor blackColor] setFill];
float ppi = [self getPPI];
if (ppi == -1.0) // unable to draw, maybe an ipad.
return;
float linesDist = ppi/25.4; // ppi/mm per inch (regular size iPad would be 132.0, iPhone6+ 154.0)
float linesWidthShort = 15.0;
float linesWidthMid = 20.0;
float linesWidthLong = 25.0;
for (float i = 0, c = 0; i <= self.bounds.size.height; i = i + linesDist, c = c +1.0)
{
bool isMid = (int)c % 5 == 0;
bool isLong = (int)c % 10 == 0;
float linesWidth = isLong ? linesWidthLong : isMid ? linesWidthMid : linesWidthShort;
UIRectFillUsingBlendMode( (CGRect){0, i, linesWidth, .5} , kCGBlendModeNormal);
/* FONT: Numbers without rotation (yes, is short)
if (isLong && i > 0 && (int)c % 10 == 0)
[[NSString stringWithFormat:#"%d", (int)(c/10)] drawAtPoint:(CGPoint){linesWidthLong +2, i -5} withAttributes:#{
NSFontAttributeName: [UIFont systemFontOfSize:9],
NSBaselineOffsetAttributeName: [NSNumber numberWithFloat:1.0]
}];
*/
// FONT: Numbers with rotation (yes, requires more effort)
if (isLong && i > 0 && (int)c % 10 == 0)
{
NSString *str = [NSString stringWithFormat:#"%d", (int)(c/10)];
NSDictionary *attrs = #{
NSFontAttributeName: [UIFont systemFontOfSize:9],
NSBaselineOffsetAttributeName: [NSNumber numberWithFloat:0.0]
};
CGSize textSize = [str sizeWithAttributes:attrs];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextRotateCTM(context, +(M_PI/2));
[str drawAtPoint:(CGPoint){i - (textSize.width/2), -(linesWidthLong + textSize.height +2)} withAttributes:attrs];
CGContextRestoreGState(context);
}
}
}
After I discovered that I needed to add the following to the top of my file I liked Matt's approach. Very simple.
#define degreesToRadian(x) (M_PI * (x) / 180.0)
mahboudz's suggestion will probably be your path of least resistance. You can rotate the UILabel 90deg with this: [label setTransform:CGAffineTransformMakeRotation(DegreesToRadians(-90.0f))]; You'll just have to calculate your cell height based upon the label width. -Matt – Matt Long Nov 10 at 0:09
Related
I'm working on one app where I need to divide a image into two part using a red line.
left part for labels
right part for prices
Question 1.
How can I draw a red line on image?
Question 2.
How can I divide image to two parts using red line ?( red line position is not fixed. user can move the position wherever it want)
Question 3.
How can I get line current position and how can I use that position two divide image
Thanks in advance
I would approach this in somewhat the same manner as koray was suggesting:
1) I am assuming that your above image/view is going to be managed by a view controller, which I will call ImageSeperatorViewController from here on.
Inside of ImageSeperatorViewController, insert koray's code in the -(void) viewDidLoad{} method. Make sure you change the imageToSplit variable to be an UIImageView instead of a plain UIView.
2) Next, I assume that you know how to detect user gestures. You will detect these gestures, and determine if the user has selected the view (i.e. bar in koray's code). Once you have determined if the user has selected bar, just update its origin's X position with the touch position.
CGRect barFrame = bar.frame;
barFrame.origin.x = *X location of the users touch*
bar.frame = barFrame;
3) For cropping, I would not use github.com/bilalmughal/NLImageCropper, it will not do what you need to do.
Try this on for size:
Header:
#interface UIImage (ImageDivider)
- (UIImage*)imageWithDividerAt:(CGFloat)position width:(CGFloat)width color:(UIColor*)color;
- (UIImage*)imageWithDividerAt:(CGFloat)position patternImage:(UIImage*)patternImage;
- (NSArray*)imagesBySlicingAt:(CGFloat)position;
#end
Implementation:
#implementation UIImage (ImageDivider)
- (UIImage*)imageWithDividerAt:(CGFloat)position patternImage:(UIImage*)patternImage
{
//pattern image
UIColor *patternColor = [UIColor colorWithPatternImage:patternImage];
CGFloat width = patternImage.size.width;
//set up context
UIGraphicsBeginImageContext(self.size);
CGContextRef context = UIGraphicsGetCurrentContext();
//draw the existing image into the context
[self drawAtPoint:CGPointZero];
//set the fill color from the pattern image color
CGContextSetFillColorWithColor(context, patternColor.CGColor);
//this is your divider's area
CGRect dividerRect = CGRectMake(position - (width / 2.0f), 0, width, self.size.height);
//the joy of image color patterns being based on 0,0 origin! must set phase
CGContextSetPatternPhase(context, CGSizeMake(dividerRect.origin.x, 0));
//fill the divider rect with the repeating pattern from the image
CGContextFillRect(context, dividerRect);
//get your new image and viola!
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
- (UIImage*)imageWithDividerAt:(CGFloat)position width:(CGFloat)width color:(UIColor *)color
{
//set up context
UIGraphicsBeginImageContext(self.size);
CGContextRef context = UIGraphicsGetCurrentContext();
//draw the existing image into the context
[self drawAtPoint:CGPointZero];
//set the fill color for your divider
CGContextSetFillColorWithColor(context, color.CGColor);
//this is your divider's area
CGRect dividerRect = CGRectMake(position - (width / 2.0f), 0, width, self.size.height);
//fill the divider's rect with the provided color
CGContextFillRect(context, dividerRect);
//get your new image and viola!
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
- (NSArray*)imagesBySlicingAt:(CGFloat)position
{
NSMutableArray *slices = [NSMutableArray array];
//first image
{
//context!
UIGraphicsBeginImageContext(CGSizeMake(position, self.size.height));
//draw the existing image into the context
[self drawAtPoint:CGPointZero];
//get your new image and viola!
[slices addObject:UIGraphicsGetImageFromCurrentImageContext()];
UIGraphicsEndImageContext();
}
//second
{
//context!
UIGraphicsBeginImageContext(CGSizeMake(self.size.width - position, self.size.height));
//draw the existing image into the context
[self drawAtPoint:CGPointMake(-position, 0)];
//get your new image and viola!
[slices addObject:UIGraphicsGetImageFromCurrentImageContext()];
UIGraphicsEndImageContext();
}
return slices;
}
The concept is simple - you want an image with the divider drawn over it. You could just overlay a view, or override drawRect:, or any number of any solutions. I'd rather give you this category. It just uses some quick Core Graphics calls to generate an image with your desired divider, be it pattern image or color, at the specified position. If you want support for horizontal dividers as well, it is rather trivial to modify this as such. Bonus: You can use a tiled image as your divider!
Now to answer your primary question. Using the category is rather self explanatory - just call one of the two methods on your source background to generate one with the divider, and then apply that image rather than the original source image.
Now, the second question is simple - when the divider has been moved, regenerate the image based on the new divider position. This is actually a relatively inefficient way of doing it, but this ought to be lightweight enough for your purposes as well as only being an issue when moving the divider. Premature optimization is just as much a sin.
Third question is also simple - call imagesBySlicingAt: - it will return an array of two images, as generated by slicing through the image at the provided position. Use them as you wish.
This code has been tested to be functional. I strongly suggest that you fiddle around with it, not for any purpose of utility, but to better understand the mechanisms used so that next time, you can be on the answering side of things
For Crop you can try this,
UIImage *image = [UIImage imageNamed:#"yourImage.png"];
CGImageRef tmpImgRef = image.CGImage;
CGImageRef topImgRef = CGImageCreateWithImageInRect(tmpImgRef, CGRectMake(0, 0, image.size.width, image.size.height / 2.0));
UIImage *topImage = [UIImage imageWithCGImage:topImgRef];
CGImageRelease(topImgRef);
CGImageRef bottomImgRef = CGImageCreateWithImageInRect(tmpImgRef, CGRectMake(0, image.size.height / 2.0, image.size.width, image.size.height / 2.0));
UIImage *bottomImage = [UIImage imageWithCGImage:bottomImgRef];
CGImageRelease(bottomImgRef);
hope this can help you, :)
if you want to draw a line you could just use a UIView with red background and make the height the size of your image and the width around 5 pixels.
UIView *imageToSplit; //the image im trying to split using a red bar
CGRect i = imageToSplit.frame;
int x = i.origin.x + i.size.width/2;
int y = i.origin.y;
int width = 5;
int height = i.size.height;
UIView *bar = [[[UIView alloc] initWithFrame:CGRectMake(x, y, width, height)] autorelease];
bar.backgroundColor = [UIColor redColor];
[self.view addSubview:bar];
I was wondering if there is a standard method in iOS to produce the numbered bubble icon for unread messages as the ones used in mail for iphone and mac.
I'm not talking about the red dots on the application item which is done with badgevalue but about the blue bubble beside the mailboxes.
Of course one can do it manually using coregraphics but it's harder to match the dimensions and color of the standard ones used in mail etc.
here are three ways to do this, in order of difficulty..
screen shot your mail app from your iphone, send the image into photoshop, extract the blue dot and use it as an image in your app. To use it in a tableviewcell, you just set the imageView.image = [UIImage imageName:#"blueDot.png"];
same as #1, except save the image as a grayscale, this way you can use Quartz and overlay your own colors on top of it. so you can make that dot any color you want. Very cool stuff.
Use Quartz to draw the whole thing. Its really not that hard. Let me know if you would like some code for that.
OK, twist my arm... here is the code to draw your own gradient sphere... from quartz.
Make a class that inherits from UIView. add the following code
static float RADIANS_PER_DEGREE=0.0174532925;
-(void) drawInContext:(CGContextRef) context
{
// Drawing code
CGFloat radius = self.frame.size.width/2;
CGFloat start = 0 * RADIANS_PER_DEGREE;
CGFloat end = 360 * RADIANS_PER_DEGREE;
CGPoint startPoint = CGPointMake(0, 0);
CGPoint endPoint = CGPointMake(0, self.bounds.size.height);
//define our grayscale gradient.. we will add color later
CGFloat cc[] =
{
.70,.7,.7,1, //r,g,b,a of color1, as a percentage of full on.
.4,.4,.4,1, //r,g,b,a of color2, as a percentage of full on.
};
//set up our gradient
CGGradientRef gradient;
CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();
gradient = CGGradientCreateWithColorComponents(rgb, cc, NULL, sizeof(cc)/(sizeof(cc[0])*4));
CGColorSpaceRelease(rgb);
//draw the gray gradient on the sphere
CGContextSaveGState(context);
CGContextBeginPath(context);
CGContextAddArc(context, self.bounds.size.width/2, self.bounds.size.height/2, radius,start,end , 0);
CGContextClosePath(context);
CGContextClip(context);
CGContextAddRect(context, self.bounds);
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, kCGGradientDrawsBeforeStartLocation);
CGGradientRelease(gradient);
//now add our primary color. you could refactor this to draw this from a color property
UIColor *color = [UIColor blueColor];
[color setFill];
CGContextSetBlendMode(context, kCGBlendModeColor); // play with the blend mode for difference looks
CGContextAddRect(context, self.bounds); //just add a rect as we are clipped to a sphere
CGContextFillPath(context);
CGContextRestoreGState(context);
}
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
[self drawInContext:context];
}
If you want to use a graphic resource from iOS, you can find it using the UIKit-Artwork-Extractor tool. Extract everything to the desktop and find the one you want. For example, the red badge for notifications is called SBBadgeBG.png. I don't know which one you mean, so search for it yourself :P
This is what I did to use a badge, the procedure is exactly the same to show a bubble in a subview of your table:
// Badge is an image with 14+1+14 pixels width and 15+1+15 pixels height.
// Setting the caps to 14 and 15 preserves the original size of the sides, so only the pixel in the middle is stretched.
UIImage *image = [UIImage imageNamed:#"badge"];
self.badgeImage = [image stretchableImageWithLeftCapWidth:(image.size.width-1)/2 topCapHeight:(image.size.height-1)/2];
// what size do we need to show 3 digits using the given font?
self.badgeFont = [UIFont fontWithName:#"Helvetica-Bold" size:13.0];
CGSize maxStringSize = [[NSString stringWithString:#"999"] sizeWithFont:self.badgeFont];
// set the annotation frame to the max needed size
self.frame = CGRectMake(0,0,
self.badgeImage.size.width + maxStringSize.width,
self.badgeImage.size.height + maxStringSize.height);
and then override the method drawRect: of your view to paint the badge and the numbers inside:
- (void)drawRect:(CGRect)rect {
// get the string to show and calculate its size
NSString *string = [NSString stringWithFormat:#"%d",self.badgeNumber];
CGSize stringSize = [string sizeWithFont:self.badgeFont];
// paint the image after stretching it enough to acommodate the string
CGSize stretchedSize = CGSizeMake(self.badgeImage.size.width + stringSize.width,
self.badgeImage.size.height);
// -20% lets the text go into the arc of the bubble. There is a weird visual effect without abs.
stretchedSize.width -= abs(stretchedSize.width *.20);
[self.badgeImage drawInRect:CGRectMake(0, 0,
stretchedSize.width,
stretchedSize.height)];
// color of unread messages
[[UIColor yellowColor] set];
// x is the center of the image minus half the width of the string.
// Same thing for y, but 3 pixels less because the image is a bubble plus a 6px shadow underneath.
float height = stretchedSize.height/2 - stringSize.height/2 - 3;
height -= abs(height*.1);
CGRect stringRect = CGRectMake(stretchedSize.width/2 - stringSize.width/2,
height,
stringSize.width,
stringSize.height);
[string drawInRect:stringRect withFont:badgeFont];
}
I would like to create a view like the notes app on iPhone and therefor need the view to have ruled lines as per the notes app, I have done this in windows where you need to get the font metrics and then draw the lines onto the device context, has anyone done this in the UITextView if so some help would be appriciated
Subclass UITextView. Override -drawRect:
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(context, self.lineColor.CGColor);
CGContextSetLineWidth(context, self.lineWidth);
CGFloat strokeOffset = (self.lineWidth / 2);
CGFloat rowHeight = self.font.lineHeight;
if (rowHeight > 0) {
CGRect rowRect = CGRectMake(self.contentOffset.x, - self.bounds.size.height, self.contentSize.width, rowHeight);
while (rowRect.origin.y < (self.bounds.size.height + self.contentSize.height)) {
CGContextMoveToPoint(context, rowRect.origin.x + strokeOffset, rowRect.origin.y + strokeOffset);
CGContextAddLineToPoint(context, rowRect.origin.x + rowRect.size.width + strokeOffset, rowRect.origin.y + strokeOffset);
CGContextDrawPath(context, kCGPathStroke);
rowRect.origin.y += rowHeight;
}
}
}
When you init the text view, be sure to set the contentMode to UIViewContentModeRedraw. Otherwise the lines won't scroll with the text.
self.contentMode = UIViewContentModeRedraw;
This isn't perfect. Ideally you should just draw into the rect that's passed. But I was lazy and this worked for my needs.
I think this works OK but I feel it has been hacked and I do not fully undestand the mechanism of the UITextView class;
first you must add the following to your delegate to force a redraw on scrolling
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
// NSLog(#"scrollViewDidScroll The scroll offset is ---%f",scrollView.contentOffset.y);
[noteText setNeedsDisplay];
}
then implement drawRect in the subclass as so
- (void)drawRect:(CGRect)rect {
// Drawing code
// Get the graphics context
CGContextRef ctx = UIGraphicsGetCurrentContext();
[super drawRect:rect];
// Get the height of a single text line
NSString *alpha = #"ABCD";
CGSize textSize = [alpha sizeWithFont:self.font constrainedToSize:self.contentSize lineBreakMode:UILineBreakModeWordWrap];
NSUInteger height = textSize.height;
// Get the height of the view or contents of the view whichever is bigger
textSize = [self.text sizeWithFont:self.font constrainedToSize:self.contentSize lineBreakMode:UILineBreakModeWordWrap];
NSUInteger contentHeight = (rect.size.height > textSize.height) ? (NSUInteger)rect.size.height : textSize.height;
NSUInteger offset = 6 + height; // MAGIC Number 6 to offset from 0 to get first line OK ???
contentHeight += offset;
// Draw ruled lines
CGContextSetRGBStrokeColor(ctx, .8, .8, .8, 1);
for(int i=offset;i < contentHeight;i+=height) {
CGPoint lpoints[2] = { CGPointMake(0, i), CGPointMake(rect.size.width, i) };
CGContextStrokeLineSegments(ctx, lpoints, 2);
}
}
Still worry about this Magic Number 6
Bob
You can try setting the backgroundColor of you textView using an image with ruled lines
textView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:#"RuledLinesPage.png"]];
Color with pattern image creates a tiled image if the area to be filled with the color is larger than the image. So you will have to make sure that the image size is correct size/tileable (I don't think 'tileable' is a real word but i hope you get what i mean). Also you will have to create the image with ruled lines to best match you textView's font.
Good Luck.
#lukya,
Your solution is bit messy as when we scroll the UITextView the text only scrolls leaving the lines (coming from the image) in its place.
A better solution would be to add subview to your text view where you have drawn the lines. You need to add an observer to the text view in order to track its change in content size as the text increase/decrease.
I don't know anything about graphics or drawing so I assume that's why I can't figure out what to look for to solve this.
Here's what I got in my UITableViewCell's drawRect
- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(ctx, 0.0, 0.0, 0.0, 1.0);
CGContextSetLineWidth(ctx, 0.25);
for (int i = 0; i < [columns count]; i++) {
CGFloat f = [((NSNumber*) [columns objectAtIndex:i]) floatValue];
CGContextMoveToPoint(ctx, f, 0);
CGContextAddLineToPoint(ctx, f, self.bounds.size.height);
}
CGContextStrokePath(ctx);
}
I think this should be drawing a black line but the line is gray, blending with what's in the background. How can I draw a solid line that is not influenced by a background image? I've tried all the blend mode's thinking maybe one would be like a blend mode none, because I don't want any blending, but all draw lines that blend in some way with the background.
You can try turning off antialiasing using CGContextSetShouldAntialias(). Also, 0.25 seems like a pretty thin line. Setting it to 1.0 might give you what you're looking for.
Two problems:
* You're drawing a black line that's 0.25 pixels (or 0.5 pixels on iPhone 4) wide; antialiasing will make this appear semi-transparent. Try setting the line width to 1.
* If f is an integer, then the center of the line is aligned on a pixel boundary (you want it on a pixel center). Try adding 0.5f.
If you want thinner lines on iPhone 4, then check if self.layer.scale == 2 and if so, set the line width to 0.5 and add 0.25f.
Alternatively, set the fill colour and call CGContextFillRect() instead, which means you don't have to worry about pixel centers.
UIView *line = [[UIView alloc]initWithFrame:CGRectMake(100,0,1,44)];
line.backgroundColor = [UIColor colorWithRed:244.0f/255.0f green:244.0f/255.0f blue:244.0f/255.0f alpha:1];
[cell addSubview:line];
It seems that none of these solutions eliminate the lag associated with rendering images onto the screen (whether from .png's or using CG).
There is a 28x16 grid of blocks that are each 16x16 pixels, and at some points in the game, about half of them need to change their image because of a state change. Having each block as a subview of the main view causes a lag when half of them need to individually change their image (either from .png's or using CG).
I tried having one "map" view with whose drawRect: method is:
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, rect);
// width and height are defined as the width and height of the grid (28x16 for iPhone)
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
// states[] is an enum instance variable that holds the states of each block in the map (state determines image)
if (states[(x * height) + y] == PXBlockStateEmpty) {
CGContextSetFillColorWithColor(context, [UIColor colorWithRed:153.0/255.0 green:153.0/255.0 blue:153.0/255.0 alpha:0.5].CGColor);
CGContextSetStrokeColorWithColor(context, [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.5].CGColor);
CGContextAddRect(context, CGRectMake(x * 16, y * 16, 16, 16));
CGContextDrawPath(context, kCGPathFillStroke);
} else if (states[(x * height) + y] == PXBlockStateSolid || states[(x * height) + y] == PXBlockStateSolidEdge) {
CGContextSetFillColorWithColor(context, [UIColor colorWithRed:0.0 green:0.0 blue:102.0/255.0 alpha:0.9].CGColor);
CGContextSetStrokeColorWithColor(context, [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.5].CGColor);
CGContextAddRect(context, CGRectMake(x * 16, y * 16, 16, 16));
CGContextDrawPath(context, kCGPathFillStroke);
} else if (states[(x * height) + y] == PXBlockStateBuilding) {
CGContextSetFillColorWithColor(context, [UIColor colorWithRed:51.0/255.0 green:51.0/255.0 blue:51.0/255.0 alpha:0.5].CGColor);
CGContextFillRect(context, CGRectMake(x * 16, y * 16, 16, 16));
}
}
}
So my solution was to call setNeedsDisplayInRect: on the map, passing the frame (a 16x16 rect) of the block whose state changed. Am I using setNeedsDisplayInRect: incorrectly, or is this just an inefficient way to do it?
Both options (one subview vs hundreds of subviews) lag the game for a bit when a lot of the board is filled with a different image, and the second solution in particular lags whenever ANY block's image needs to be updated.
Any ideas? Thank you for your help!
Calling setNeedsDisplayInRect: affects the argument to drawRect: but is otherwise the same as setneedsDisplay. The rectangle drawRect: receives is the union of all dirty rectangles. If you only draw content that intersects that rectangle, leaving other content untouched, you may see a speed improvement. Judging from the code snippet above you draw every tile every time. Since it is a union, you might also track dirty tiles separately and only draw dirty tiles. In that case, call CGContextClearRect for individual tiles instead of clearing the whole context, unless they are all dirty.
CGContextAddRect adds a rectangle to a path that will be drawn. Since you draw the path at every loop without beginning a new path, you redraw areas as the loop progresses. It would probably be faster to use CGContextFillRect and CGContextStrokeRect instead of a path.
Making each tile a separate UIView incurs more overhead than drawing as a whole. You should be able to get better speed from this method once the kinks are worked out.