1、根据UIView对象生成UIImage对象
/**
根据UIView生成相应的UIImage对象，生成的UIImage对象的size即为view的size大小，方向为UIImageOrientationUp，即默认方向
@param view 视图
@return UIImage对象
*/
+ (UIImage *)imageWithView:(UIView *)view
{
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
2、生成纯色的UIImage对象，即根据颜色生成UIImage
/**
根据颜色和size大小生成UIImage对象，生成的UIImage对象大小即为参数imageSize的大小，颜色即为参数color的颜色，方向为UIImageOrientationUp，即默认方向
@param color 颜色
@param imageSize 大小
@return UIImage对象
*/
+ (UIImage *)imageWithColor:(UIColor *)color size:(CGSize)imageSize
{
CGRect rect = CGRectMake(0, 0, imageSize.width, imageSize.height);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [color CGColor]);
CGContextFillRect(context, rect);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
3、对UIImage对象进行剪裁操作
/**
剪裁图片到指定的rect，rect决定了剪裁图片的左上角的坐标，和剪裁的大小
@param rect 坐标大小
@return UIImage对象
*/
- (UIImage *)imageCropToRect:(CGRect)rect
{
CGRect drawRect = CGRectMake(-rect.origin.x , -rect.origin.y, self.size.width * self.scale, self.size.height * self.scale);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, CGRectMake(0, 0, rect.size.width, rect.size.height));
[self drawInRect:drawRect];
UIImage *tempImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return tempImage;
}
//此方法与上面的方法效果一样，只不过使用的是相对比较底层的框架，是CGImage的范畴，但是论结果应该是一样的
//有不同的地方是，当你处理图片设计方向问题的时候，这个C语言的处理不是很友好，个人理解的是，CGImage这个框架不涉及方向的处理，所以这个方法还是慎重考虑使用。
- (UIImage *)imageCropToRect:(CGRect)rect
{
CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, rect.size.height));
UIImage *tempImage = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return tempImage;
}
4、对UIImage对象进行缩放操作，即按比例缩放到指定的大小
/**
缩放图片大小到指定size
@param size 大小
@return UIImage对象
*/
- (UIImage*)imageScaleToSize:(CGSize)size
{
UIGraphicsBeginImageContext(size);
[self drawInRect:CGRectMake(0 ,0 ,size.width ,size.height)];
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
5、修正图片的方向
/* 修正图片方向(应该只有在拍照完成使用照片的时候会用到) */
- (UIImage *)imageFixOrientation
{
// No-op if the orientation is already correct
if (self.imageOrientation == UIImageOrientationUp) return self;
// We need to calculate the proper transformation to make the image upright.
// We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
CGAffineTransform transform = CGAffineTransformIdentity;
switch (self.imageOrientation) {
case UIImageOrientationDown:
case UIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height);
transform = CGAffineTransformRotate(transform, M_PI);
break;
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
transform = CGAffineTransformTranslate(transform, self.size.width, 0);
transform = CGAffineTransformRotate(transform, M_PI_2);
break;
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, 0, self.size.height);
transform = CGAffineTransformRotate(transform, -M_PI_2);
break;
case UIImageOrientationUp:
case UIImageOrientationUpMirrored:
break;
}
switch (self.imageOrientation) {
case UIImageOrientationUpMirrored:
case UIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, self.size.width, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
case UIImageOrientationLeftMirrored:
case UIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, self.size.height, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
case UIImageOrientationUp:
case UIImageOrientationDown:
case UIImageOrientationLeft:
case UIImageOrientationRight:
break;
}
// Now we draw the underlying CGImage into a new context, applying the transform
// calculated above.
CGContextRef ctx = CGBitmapContextCreate(NULL, self.size.width, self.size.height,
CGImageGetBitsPerComponent(self.CGImage), 0,
CGImageGetColorSpace(self.CGImage),
CGImageGetBitmapInfo(self.CGImage));
CGContextConcatCTM(ctx, transform);
switch (self.imageOrientation) {
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
// Grr...
CGContextDrawImage(ctx, CGRectMake(0,0,self.size.height,self.size.width), self.CGImage);
break;
default:
CGContextDrawImage(ctx, CGRectMake(0,0,self.size.width,self.size.height), self.CGImage);
break;
}
// And now we just create a new UIImage from the drawing context
CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
UIImage *img = [UIImage imageWithCGImage:cgimg];
CGContextRelease(ctx);
CGImageRelease(cgimg);
return img;
}
6、图片质量的压缩
//通常我们使用下面的方法对图片进行压缩处理
//但是对于下面这个系统的方法开说，压缩系数需要一个合适的值，我当时记得是各种测试测出来一个比较合适的值
//不知道大家对于这个压缩系数有什么理解，还请指点一二
/**
图片压缩
@param image UIImage图片对象
@return compressionQuality 压缩系数0-1之间的数值
*/
UIImageJPEGRepresentation(image, compressionQuality);
