颜色空间
cmyk印刷行业
RGB
渐变颜色：线性渐变,环状渐变
线性渐变：渐变的区域是当前context，垂直于startPoint <-> endPoint线段，并且于这条线段相交的直线
环状渐变：
corefoundation(c) -- foundation(oc)转换
强制转换：__bridge id(类型)
/****/自动引用计数
将绘制图片保存起来
创建image context -- 获取画布 -- …… -- 获取图片 -- 保存图片 -- 结束绘制
压缩成图片：
png(无损压缩)
jpg(有损压缩)
#import "LinearGradient.h"
@implementation LinearGradient
//线性渐变
- (void)drawRect:(CGRect)rect {
CGContextRef context =
UIGraphicsGetCurrentContext();
CGColorSpaceRef colorSpace =
CGColorSpaceCreateDeviceRGB();
//颜色的分量表示
CGFloat components[] = {1.0,
0.0, 0.0,
1.0, 0.0, 0.0,
1.0, 1.0,
0.0, 1.0, 0.0,
1.0};
//颜色的位置
CGFloat locations[] = {1.0,
0.0, 0.5};
CGGradientRef gradient =
CGGradientCreateWithColorComponents(colorSpace, components, locations,
3);
//渐变的区域是当前context，垂直于startPoint <-> endPoint线段，并且于这条线段相交的直线
CGContextDrawLinearGradient(context, gradient,
CGPointMake(100,
0),
CGPointMake(200,
0),
0);
CGFloat locations2[] = {0.4,
1.0};
CGGradientRef gradient2 =
CGGradientCreateWithColorComponents(colorSpace, components, locations2,
2);
//渐变的区域是当前context，垂直于startPoint <-> endPoint线段，并且于这条线段相交的直线
CGContextDrawLinearGradient(context, gradient2,
CGPointMake(210,
0),
CGPointMake(310,
0),
0);
}
@end
#import "RadialGradientView.h"
@implementation RadialGradientView
//环状渐变
- (void)drawRect:(CGRect)rect {
CGContextRef context =
UIGraphicsGetCurrentContext();
CGColorSpaceRef colorSpace =
CGColorSpaceCreateDeviceRGB();
NSArray *array = @[(__bridge
id)[UIColor
redColor].CGColor, (__bridge
id)[UIColor
blueColor].CGColor, (__bridge
id)[UIColor
purpleColor].CGColor];
CGFloat locations[] = {0.0,
0.5, 1.0};
CGGradientRef gradient =
CGGradientCreateWithColors(colorSpace, (__bridge
CFArrayRef)array, locations);
CGContextDrawRadialGradient(context, gradient,
CGPointMake(200,
200),
0, CGPointMake(150,
200),
100, 0);
}
@end
//将绘制图片保存
#import "ViewController.h"
@interface
ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super
viewDidLoad];
UIGraphicsBeginImageContext(CGSizeMake(200,
200));
CGContextRef context =
UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [UIColor
yellowColor].CGColor);
CGContextFillRect(context,
CGRectMake(0,
0, 100,
100));
UIImage *image =
UIGraphicsGetImageFromCurrentImageContext();
NSData *data =
UIImageJPEGRepresentation(image, 1.0);
// NSData *data = UIImagePNGRepresentation(image);
[data writeToFile:@"/Users/apple/desktop/image.jpg"
atomically:YES];
UIGraphicsEndImageContext();
}
- (void)didReceiveMemoryWarning {
[super
didReceiveMemoryWarning];
}
@end