CorePlot：用图片定制坐标轴标签
原文：http://stackoverflow.com/questions/6748996/how-to-set-custom-tick-marks-in-core-plot-to-icons
Axis label 可以使用任何 CPTLayer（CALayer 子类）作为标签。用UIImage 作为 CPTLayer 的背景层即可定制轴标签。有许多Core Plot 的使用定制轴标签的例子，虽然他们用的是文本标签。
有两种方法定制图形类的轴标签：
1、 graph的labeling policy设置为CPTAxisLabelingPolicyNone。创建NSSet，放入所有 AxisLabel，然后将坐标轴的 axisLabels 属性设置为 NSSet。如果用这种方法，你需要提供major/minor tick的location。
2、labeling policy 设置为其他策略，以产生 major/minor tick。然后实现axis:shouldUpdateAxisLabelsAtLocations:委托方法。在方法中，在指定的location创建新的label 然后返回 No 以忽略默认的标签。
Jul 19 '11 at 22:46
Eric Skroch
根据 Eric 的说法，我编写了一些代码，以供参考：
if (yAxisIcons) {
int custonLabelsCount = [self.yAxisIcons count];
NSMutableArray *customLabels =[NSMutableArray arrayWithCapacity:custonLabelsCount];
for (NSUInteger i = 0; i <custonLabelsCount; i++)
{
NSNumber*tickLocation = [NSNumber numberWithInt:i];
NSString *file =[yAxisIcons objectAtIndex:i];
UIImage *icon =[UIImage imageNamed:file];
CPImageLayer*layer; // My custom CPLayer subclass - see code below
CGFloatnativeHeight = 1;
CGFloatnativeWidth = 1;
if (icon) {
layer = [[CPImageLayer alloc] initWithImage:icon];
nativeWidth = 20;//CGImageGetWidth(icon.CGImage);
nativeHeight = 20;//CGImageGetHeight(icon.CGImage);
//layer.contents = (id)icon.CGImage;
if (nativeWidth > biggestCustomIconWidth) {
biggestCustomIconWidth = nativeWidth;
}
}else{
layer= [[CPImageLayer alloc] initWithFrame:CGRectMake(0, 0, 1, 1)];
}
CGRect startFrame = CGRectMake(0.0, 0.0,nativeWidth, nativeHeight);
layer.frame= startFrame;
layer.backgroundColor = [UIColor clearColor].CGColor;
CPAxisLabel *newLabel = [[CPAxisLabel alloc]initWithContentLayer:layer];
newLabel.tickLocation = [tickLocation decimalValue];
newLabel.offset = x.labelOffset +x.majorTickLength; [customLabels addObject:newLabel];
[newLabel release];
[layer release];
}
y.axisLabels = [NSSetsetWithArray:customLabels];
}
CPImageLayer.h
#import "CPLayer.h"
@interface CPImageLayer : CPLayer {
UIImage*_image;
}
-(id)initWithImage:(UIImage *)image; @end
CPImageLayer.m
#import "CPImageLayer.h" #import "CPLayer.h"
@implementation CPImageLayer
-(void)dealloc{
[_imagerelease];
[super dealloc];
}
-(id)initWithImage:(UIImage *)image{
CGRect f =CGRectMake(0, 0, image.size.width, image.size.height);
if (self =[super initWithFrame:f]) {
_image = [imageretain];
}
return self;
}
-(void)drawInContext:(CGContextRef)ctx{
CGContextDrawImage(ctx, self.bounds, _image.CGImage);
}
@end
Jul 22 '11 at 14:01
Lukasz