#import <UIKit/UIKit.h>

@interface UIColor (RandomColor)
+(UIColor *) randomColor;
@end


#import "UIColor+RandomColor.h"

@implementation UIColor (RandomColor)

+(UIColor *) randomColor
{
    CGFloat hue = ( arc4random() % 256 / 256.0 );  //0.0 to 1.0
    CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5;  // 0.5 to 1.0,away from white
    CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5;  //0.5 to 1.0,away from black
        return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
@end


将随机生成的颜色绘制成图片。

-(void)createImage
{

    NSString* path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES) objectAtIndex:0];

    path = @"/Users/shouqiangwei/Desktop/未命名文件夹 2";
    NSLog(@"path = %@",path);
    NSString *imgName;
    NSString *imgURL;
    NSString *markNum;
    UIImage *img;
    NSData *imgData;
    NSError *err;
    int width= 1000, height=1000, fontSize;
    CGPoint markPoint;
    int baseLength = 320;
    NSFileManager *fm = [NSFileManagerdefaultManager];
    for (int i=0; i<1000; i++) {

        UIColor *color = [UIColorrandomColor];
        [_currentColorImageViewsetBackgroundColor:color];

        imgName = [NSString stringWithFormat:@"%i.jpg", i+1];
        _lblCount.text = imgName;

        imgURL = [path stringByAppendingPathComponent:imgName];
        if (![fm fileExistsAtPath:imgURL]) {
            const CGFloat *colorComps = CGColorGetComponents(color.CGColor);
            markNum = [NSString stringWithFormat:@"%i", i+1];

            fontSize = width / 5;
            markPoint = CGPointMake(fontSize/2, fontSize/2);

            UIGraphicsBeginImageContext(CGSizeMake(width, height));
            CGContextRef ctx =UIGraphicsGetCurrentContext();
            CGContextSetRGBFillColor(ctx, colorComps[0], colorComps[1], colorComps[2], colorComps[3]);
            CGContextFillRect(ctx, CGRectMake(0, 0, width, height));
            CGContextSetRGBFillColor(ctx, 1.0, 1.0, 1.0,1.0);

            //创建图片上的数字。
            [markNum drawAtPoint:markPoint withFont:[UIFont systemFontOfSize:fontSize]];
            img = UIGraphicsGetImageFromCurrentImageContext();
            self.imageView.image= img;
            UIGraphicsEndImageContext();


            //创建到本地。
            imgData = [NSDatadataWithData:UIImageJPEGRepresentation(img,1.0f)];

            [imgData writeToFile:imgURLoptions:NSDataWritingAtomicerror:&err];

            if (err) {
                NSLog(@"error: %@\nimage:%@", err.localizedDescription, imgName);
            } else {
                NSLog(@"done: %@", imgName);
            }
        }
    }

}