在自定义NSTextFieldCell中调整NSImage的大小

Question

我使用Apple的示例创建了拖放应用程序：https://developer.apple.com/library/mac/samplecode/SourceView/Introduction/Intro.html

我加载了拖动文件的实际图像。

当我将此图像文件拖到我的 NSOutlineView 中时，我看到它以这种方式调整大小：

我没有任何修改地使用Apple的 ImageAndTextCell 类来定制NSTextFieldCell。

我如何调整此图像的大小以适合按比例缩小？

Answer 1

完美无缺。

@implementation NSImage (ProportionalScaling)

- (NSImage*)imageByScalingProportionallyToSize:(NSSize)targetSize
{
  NSImage* sourceImage = self;
  NSImage* newImage = nil;

  if ([sourceImage isValid])
  {
    NSSize imageSize = [sourceImage size];
    float width  = imageSize.width;
    float height = imageSize.height;

    float targetWidth  = targetSize.width;
    float targetHeight = targetSize.height;

    float scaleFactor  = 0.0;
    float scaledWidth  = targetWidth;
    float scaledHeight = targetHeight;

    NSPoint thumbnailPoint = NSZeroPoint;

    if ( NSEqualSizes( imageSize, targetSize ) == NO )
    {

      float widthFactor  = targetWidth / width;
      float heightFactor = targetHeight / height;

      if ( widthFactor < heightFactor )
        scaleFactor = widthFactor;
      else
        scaleFactor = heightFactor;

      scaledWidth  = width  * scaleFactor;
      scaledHeight = height * scaleFactor;

      if ( widthFactor < heightFactor )
        thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;

      else if ( widthFactor > heightFactor )
        thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
    }

    newImage = [[NSImage alloc] initWithSize:targetSize];

    [newImage lockFocus];

      NSRect thumbnailRect;
      thumbnailRect.origin = thumbnailPoint;
      thumbnailRect.size.width = scaledWidth;
      thumbnailRect.size.height = scaledHeight;

      [sourceImage drawInRect: thumbnailRect
                     fromRect: NSZeroRect
                    operation: NSCompositeSourceOver
                     fraction: 1.0];

    [newImage unlockFocus];

  }

  return [newImage autorelease];
}

@end