Question

我正在从相册中挑选一张照片，不过我希望能够用它来做以下事情：

更改顶部和底部的alpha值（从顶部开20个像素，从底部开20个像素）到0.5
然后只复制中间的未更改部分并将其分配给另一个UIImageView

我有这段代码：

@synthesize imageView, croppedImageView, choosePhotoBtn, takePhotoBtn;

-(IBAction) getPhoto:(id) sender {
    UIImagePickerController * picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;

    if((UIButton *) sender == choosePhotoBtn) {
        picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
    } else {
        picker.sourceType = UIImagePickerControllerSourceTypeCamera;
    }


    [self presentModalViewController:picker animated:YES];
}



-(void) imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
    [picker dismissModalViewControllerAnimated:YES];
    [picker release];
    imageView.image = [info objectForKey:UIImagePickerControllerOriginalImage]; 

        /* then here I want to change the alpha value of the top and bottom parts */
        /* then copy the unchanged part then assign it to the image value of croppedImageView */

}

Answer 1

我认为实现这一目标的最佳方法是使用遮罩图像。您可以在此博客文章中找到一个很好的示例：http://iosdevelopertips.com/cocoa/how-to-mask-an-image.html

更改UIImageView顶部和底部的alpha值

1 个答案: