objective-c - 在目标 c 中的现有图像上渲染播放图像

Question

我有一些视频和图像的收藏视图

使用 AVFoundation 能够从 iPhone 捕获视频并使用 AVAssetImageGenerator 生成缩略图。在画廊图像中显示时，应区分它的视频缩略图。所以我需要通过在其上绘制视频符号（如播放图标）来转换精确的图像。

可能吗？

Answer 1

您可以使用CoreGraphics来编辑图像。

UIImage首先，使用您要编辑的图像创建一个。然后，做这样的事情：

UIImage *oldThumbnail; //set this to the original thumbnail image
UIGraphicsBeginImageContext(oldThumbnail.size);
[oldThumbnail drawInRect:CGRectMake(0, 0, oldThumbnail.size.width, oldThumbnail.size.height)];

/*Now there are two ways to draw the play symbol.

One would be to have a pre-rendered play symbol that you load into a UIImage and draw with drawInRect */

UIImage *playSymbol = [UIImage imageNamed:"PlaySymbol.png"];
CGRect playSymbolRect; //I'll let you figure out calculating where you should draw the play symbol
[playSymbol drawInRect: playSymbolRect];

//The other way would be to draw the play symbol directly using CoreGraphics calls.  Start with this:
CGContextRef context = UIGraphicsGetCurrentContext();

//now use CoreGraphics calls. I won't go over it here, butthe second answer to this questionmay be helpful.

//Once you have finished drawing your image, you can put it in a UIImage.
UIImage *newThumbnail = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext(); //make sure you remember to do this :)

现在你可以在 UIImageView 中使用新生成的缩略图，缓存它，这样你就不需要每次都重新渲染它，等等。

Answer 2

这应该有效（您可能必须使用位置和尺寸）：

-(UIImage*)drawPlayButton:(UIImage*)image
{
    UIImage *playButton = [UIImage imageNamed:@"playbutton.png"];
    UIGraphicsBeginImageContext(image.size);
    [image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
    [playButton drawInRect:CGRectMake(image.size.width/2-playButton.size.width/2, image.size.height/2-playButton.size.height/2, playButton.size.width, playButton.size.height)];
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return result;
}