Cocoa 核心图形中的精确像素网格覆盖?
在我创建以像素为中心的图像编辑器的实验中,我一直试图绘制一个精确的网格覆盖,以帮助用户在尝试访问某些像素时进行指导。然而,我绘制的网格不是很均匀,尤其是在较小的尺寸下。这是一个规则模式,每几个普通列中有一个稍大的列,所以我认为这是一个舍入问题,但我在代码中看不到它。这是我的密码:Cocoa 核心图形中的精确像素网格覆盖?,cocoa,core-graphics,nsimage,cgimage,Cocoa,Core Graphics,Nsimage,Cgimage,在我创建以像素为中心的图像编辑器的实验中,我一直试图绘制一个精确的网格覆盖,以帮助用户在尝试访问某些像素时进行指导。然而,我绘制的网格不是很均匀,尤其是在较小的尺寸下。这是一个规则模式,每几个普通列中有一个稍大的列,所以我认为这是一个舍入问题,但我在代码中看不到它。这是我的密码: - (void)drawRect:(NSRect)dirtyRect { context = [[NSGraphicsContext currentContext] graphicsPort];
- (void)drawRect:(NSRect)dirtyRect
{
context = [[NSGraphicsContext currentContext] graphicsPort];
CGContextAddRect(context, NSRectToCGRect(self.bounds));
CGContextSetRGBStrokeColor(context, 1.0f, 0.0f, 0.0f, 1.0f);
CGContextStrokePath(context);
CGContextSetInterpolationQuality(context, kCGInterpolationNone);
CGContextSetShouldAntialias(context, NO);
if (image)
{
NSRect imageRect = NSZeroRect;
imageRect.size = CGImageGetSize([image CGImage]);
drawRect = [self bounds];
NSRect viewRect = drawRect;
CGFloat aspectRatio = imageRect.size.width / imageRect.size.height;
if (viewRect.size.width / viewRect.size.height <= aspectRatio)
{
drawRect.size.width = viewRect.size.width;
drawRect.size.height = imageRect.size.height * (viewRect.size.width / imageRect.size.width);
}
else
{
drawRect.size.height = viewRect.size.height;
drawRect.size.width = imageRect.size.width * (viewRect.size.height / imageRect.size.height);
}
drawRect.origin.x += (viewRect.size.width - drawRect.size.width) / 2.0;
drawRect.origin.y += (viewRect.size.height - drawRect.size.height) / 2.0;
CGContextDrawImage(context, drawRect, [image CGImage]);
if (showPixelGrid)
{
//Draw grid by creating start and end points for vertical and horizontal lines.
//FIXME: Grid is uneven, especially at smaller sizes.
CGContextSetStrokeColorWithColor(context, CGColorGetConstantColor(kCGColorBlack));
CGContextAddRect(context, drawRect);
CGContextStrokePath(context);
NSUInteger numXPoints = (NSUInteger)imageRect.size.width * 2;
NSUInteger numYPoints = (NSUInteger)imageRect.size.height * 2;
CGPoint xPoints[numXPoints];
CGPoint yPoints[numYPoints];
CGPoint startPoint;
CGPoint endPoint;
CGFloat widthRatio = drawRect.size.width / imageRect.size.width;
CGFloat heightRatio = drawRect.size.height / imageRect.size.height;
startPoint.x = drawRect.origin.x;
startPoint.y = drawRect.origin.y;
endPoint.x = drawRect.origin.x;
endPoint.y = drawRect.size.height + drawRect.origin.y;
for (NSUInteger i = 0; i < numXPoints; i += 2)
{
startPoint.x += widthRatio;
endPoint.x += widthRatio;
xPoints[i] = startPoint;
xPoints[i + 1] = endPoint;
}
startPoint.x = drawRect.origin.x;
startPoint.y = drawRect.origin.y;
endPoint.x = drawRect.size.width + drawRect.origin.x;
endPoint.y = drawRect.origin.y;
for (NSUInteger i = 0; i < numYPoints; i += 2)
{
startPoint.y += heightRatio;
endPoint.y += heightRatio;
yPoints[i] = startPoint;
yPoints[i + 1] = endPoint;
}
CGContextStrokeLineSegments(context, xPoints, numXPoints);
CGContextStrokeLineSegments(context, yPoints, numYPoints);
}
}
}
-(void)drawRect:(NSRect)dirtyRect
{
上下文=[[NSGraphicsContext currentContext]GraphicsSport];
CGContextAddRect(上下文,NSRectToCGRect(self.bounds));
CGContextSetRGBStrokeColor(上下文,1.0f,0.0f,0.0f,1.0f);
CGContextStrokePath(上下文);
CGContextSetInterpolationQuality(上下文,kCGInterpolationNone);
CGContextSetShouldAntialias(上下文,否);
如果(图像)
{
NSRect imageRect=NSZeroRect;
imageRect.size=CGImageGetSize([image CGImage]);
drawRect=[自边界];
NSRect viewRect=drawRect;
CGFloat aspectRatio=imageRect.size.width/imageRect.size.height;
if(viewRect.size.width/viewRect.size.height更新:我通过一些调整使您的代码运行-CGImageGetSize()在哪里从哪里来?-我真的看不出问题所在,除了列的大小不是都非常小。这就是它的工作原理。唯一的解决方法是将缩放比例固定为图像大小的整数倍-换句话说,使图像大小的最大整数倍小于视图大小-或者减少屏幕上以非常小的尺寸绘制的线的数量,以消除这一伪影。这是因为在大多数编辑器中,像素网格只有在长距离放大时才可见。更不用说,如果网格仍以3-4倍分辨率可见,则会使视图过于繁忙
我无法运行您提供的代码,因为其中有一堆类IVAR,但粗略地看,我会说这与绘制像素边界有关。在您舍入到整数以去除模糊AA人工制品后(我注意到您关闭了AA,但理想情况下,您不必这样做),然后需要向原点添加0.5,以便在像素的中心绘制线,而不是在边界上绘制线
像这样:
+---X---+---+---+---+---+
| | | | Y | | |
+---+---+---+---+---+---+
X : CGPoint (1, 1)
Y : CGPoint (3.5, 0.5)
您希望从像素的中心绘制,因为否则,您的线跨越两个像素
换句话说,在设置xpoint和ypoint时,请确保使用floor()或round()请输入您的值,然后添加0.5。谢谢,我会尝试一下。CGImageGetSize只是我编写的一个方便的函数。我会看看手动取整和添加.5是否达到我想要的效果。否则我可能只希望您建议并锁定缩放到整数。正如您所说,除非我将视图限制为整数,否则轻微的不均匀似乎是不可避免的谢谢。