图片的水印
开启一个基于位图的图形上下文
void UIGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque,
CGFloat scale)
从上下文中取得图片（UIImage）
UIImage* UIGraphicsGetImageFromCurrentImageContext();
结束基于位图的图形上下文
void UIGraphicsEndImageContext();
- (void)testWater
{
UIImage *bgImage = [UIImage
imageNamed:@"scene"];
//
上下文
:
基于位图(bitmap) ,
所有的东西需要绘制到一张新的图片上去
// 1.创建一个基于位图的上下文(开启一个基于位图的上下文)
// size :
新图片的尺寸
// opaque : YES :
不透明, NO :
透明
//
这行代码过后.就相当于常见一张新的bitmap,也就是新的UIImage对象
UIGraphicsBeginImageContextWithOptions(bgImage.size,
NO,
0.0);
// 2.画背景
[bgImage
drawInRect:CGRectMake(0,
0, bgImage.size.width,
bgImage.size.height)];
// 3.画右下角的水印
UIImage *waterImage = [UIImage
imageNamed:@"logo"];
CGFloat scale =
0.2;
CGFloat margin =
5;
CGFloat waterW = waterImage.size.width
* scale;
CGFloat waterH = waterImage.size.height
* scale;
CGFloat waterX = bgImage.size.width
- waterW - margin;
CGFloat waterY = bgImage.size.height
- waterH - margin;
[waterImage
drawInRect:CGRectMake(waterX, waterY, waterW,
waterH)];
// 4.从上下文中取得制作完毕的UIImage对象
UIImage *newImage =
UIGraphicsGetImageFromCurrentImageContext();
// 5.结束上下文
UIGraphicsEndImageContext();
// 6.显示到UIImageView
self.iconView.image
= newImage;
// 7.将image对象压缩为PNG格式的二进制数据
NSData *data =
UIImagePNGRepresentation(newImage);
// 8.写入文件
NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask,
YES)
lastObject]
stringByAppendingPathComponent:@"new.png"];
[data
writeToFile:path
atomically:YES];
}