在NSView中绘制图像

Question

我有一个简单的Obj C程序,目前,它允许你加载图像,绘制它,理论上应该让你缩放和旋转.我正在使用NSAffineTranslations.

我希望图像锁定在左上角(与左下角的PS/PDF标准相对),所以我使用isFlipped,并调用[afTrans scaleXBy:1.0 yBy:-1.0];

问题在于,由于某种原因,在第一次调用drawRect之后,转换不会发生.

当我加载图像时,它会出现,看起来是正确的.如果我改变窗口的大小(调用drawRect),图像会绘制,但是会颠倒并反转.这意味着转换没有生效.我没有看到第二次任何数据有任何差异.

这是代码的精简版本:

- (void)drawRect:(NSRect)rect 
{
    // Drawing code here.

//    NSLog(@"window type: %d", [[self window] backingType]);
   NSAffineTransform *afTrans = [[NSAffineTransform alloc] init];
   NSGraphicsContext *context = [NSGraphicsContext currentContext];
   NSSize sz;
   NSRect windowFrame = [[self window] frame];
   NSRect cv =[[[self window] contentView] frame];
   float deltaX, deltaY;
   NSSize superSize = [[self superview] frame].size;
   float height, width, sHeight, sWidth;

   NSRect imageRect;

   sz = [ image size];
   imageRect.size = sz;
   imageRect.origin = NSZeroPoint;

   height = sz.height  ;
   width = sz.width  ;

//    sHeight and sWidth are the hieght and with of the super-view. ie,
//    the size of the whole window view including the space for the
//    scroll bars, etc, but not including the panel or the borders,
   sHeight = superSize.height;
   sWidth = superSize.width;

   [context saveGraphicsState];

   deltaX = 0;
   deltaY = 0;

   deltaY += height; // account for flipping

   [afTrans translateXBy:deltaX yBy:deltaY];

   [afTrans scaleXBy:1.0 yBy:-1.0];

   [afTrans concat];

   NSRect drawingRect = imageRect;
   NSRect frame = imageRect;
   [self setFrame:frame];

   [image drawInRect:drawingRect
         fromRect:imageRect
         operation:NSCompositeSourceOver
         fraction:1];

   [afTrans release];
   [context restoreGraphicsState];
}

ETA:这里有一些可能相关的代码.

-(void )setImage:( NSImage * )newImage
{
    [newImage retain];
    [image release];

    rotation = 0;

    zoom = 1.0;

    image = newImage;
    NSSize imageSize = [newImage size];
    NSRect tFrame = [self frame];
    tFrame = [[self window] frame];

    tFrame.size.width = MAX(tFrame.size.width, imageSize.width);
    tFrame.size.height = MAX(tFrame.size.height, imageSize.height);
    [self setFrame:tFrame];

    [self setNeedsDisplay:YES];
}

Answer 1

我不确定你想要实现什么,但是如果你想在NSView中绘制图像并将其保留在左上角,你可以在NSView子类中做一些更简单的事情:

- (BOOL)isFlipped
{
    return YES;
}

- (void)setImage:(NSImage *)newImage
{
    [newImage retain];
    [image release];
    image = newImage;

    [image setFlipped:YES];
    [self setNeedsDisplay:YES];
}

- (void)drawRect:(NSRect)rect
{
    [image drawAtPoint:NSZeroPoint fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1];

    // Or stretch image to fill view
    //[image drawInRect:[self bounds] fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1];
}

通过删除[self setFrame:...];drawRect和setImage方法中的调用,我也能够通过代码获得类似的结果.