ios二维绘图之颜色渐变

#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

//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