我想在NSImage上添加十字架,这是我的代码:
-(NSSize)convertPixelSizeToPointSize:(NSSize)px
{
CGFloat displayScale = [[NSScreen mainScreen] backingScaleFactor];
NSSize res;
res.width = px.width / displayScale;
res.height = px.height / displayScale;
return res;
}
-(void)awakeFromNib
{
CGFloat scale = [[NSScreen mainScreen] backingScaleFactor];
NSLog(@"backingScaleFactor : %f",scale);
NSImage *img = [[[NSImage alloc]initWithContentsOfFile:@"/Users/support/Pictures/cat.JPG"] autorelease];
NSBitmapImageRep *imgRep = [NSBitmapImageRep imageRepWithData:[img TIFFRepresentation]];
NSSize imgPixelSize = NSMakeSize([imgRep pixelsWide],[imgRep pixelsHigh]);
NSSize imgPointSize = [self convertPixelSizeToPointSize:imgPixelSize];
[img setSize:imgPointSize];
NSLog(@"imgPixelSize.width: %f , imgPixelSize.height:%f",imgPixelSize.width,imgPixelSize.height);
NSLog(@"imgPointSize.width: %f , imgPointSize.height:%f",imgPointSize.width,imgPointSize.height);
[img lockFocus];
NSAffineTransform *trans = [[[NSAffineTransform alloc] init] autorelease];
[trans scaleBy:1.0 / scale];
[trans set];
NSBezierPath *path = [NSBezierPath bezierPath];
[[NSColor redColor] setStroke];
[path moveToPoint:NSMakePoint(0.0, 0.0)];
[path lineToPoint:NSMakePoint(imgPixelSize.width, imgPixelSize.height)];
[path moveToPoint:NSMakePoint(0.0, imgPixelSize.height)];
[path lineToPoint:NSMakePoint(imgPixelSize.width, 0.0)];
[path setLineWidth:1];
[path stroke];
[img unlockFocus];
[imageView setImage:img];
imgRep = [NSBitmapImageRep imageRepWithData:[img TIFFRepresentation]];
NSData *imageData = [imgRep representationUsingType:NSJPEGFileType properties:nil];
[imageData writeToFile:@"/Users/support/Pictures/11-5.JPG" atomically:NO];
}
在非视网膜显示器上结果是:
和控制台显示:
2012-07-06 00:53:09.889 RetinaTest[8074:403] backingScaleFactor : 1.000000
2012-07-06 00:53:09.901 RetinaTest[8074:403] imgPixelSize.width: 515.000000 , imgPixelSize.height:600.000000
2012-07-06 00:53:09.902 RetinaTest[8074:403] imgPointSize.width: 515.000000 , imgPointSize.height:600.000000
但是在视网膜显示器上(我没有使用真正的视网膜显示器而是使用hidpi模式):
控制台:
2012-07-06 00:56:05.071 RetinaTest[8113:403] backingScaleFactor : 2.000000
2012-07-06 00:56:05.083 RetinaTest[8113:403] imgPixelSize.width: 515.000000 , imgPixelSize.height:600.000000
2012-07-06 00:56:05.084 RetinaTest[8113:403] imgPointSize.width: 257.500000 , imgPointSize.height:300.000000
如果我省略这些行:
NSAffineTransform *trans = [[[NSAffineTransform alloc] init] autorelease];
[trans scaleBy:1.0 / scale];
[trans set];
但是,如果我将[NSAffineTransform scaleBy]更改为1.0,结果是正确的
NSAffineTransform *trans = [[[NSAffineTransform alloc] init] autorelease];
[trans scaleBy:1.0];
[trans set];
控制台:
2012-07-06 01:01:03.420 RetinaTest[8126:403] backingScaleFactor : 2.000000
2012-07-06 01:01:03.431 RetinaTest[8126:403] imgPixelSize.width: 515.000000 , imgPixelSize.height:600.000000
2012-07-06 01:01:03.432 RetinaTest[8126:403] imgPointSize.width: 257.500000 , imgPointSize.height:300.000000
请问有人可以解释一下吗? hidpi模式与视网膜显示不同吗?
答案 0 :(得分:4)
我想我找到了答案。如果NSAffineTransform设置为NSImage的上下文,它会将坐标系转换为像素尺寸,即2 x点尺寸。即使它像这样是空的:
NSAffineTransform *trans = [[[NSAffineTransform alloc] init] autorelease];
[trans set];
我不知道这是一个错误还是它的工作方式。
答案 1 :(得分:0)
重置转换不是错误(指自己的答案)。使用hidpi使默认转换成为允许大多数高级代码按原样运行的转换。重置为身份变换撤消此操作以使坐标系1:1与像素对齐。
但是应该很少需要这样做。简化代码以取出图像代表和转换更改可以实现:
NSImage *img = [[[NSImage alloc]initWithContentsOfFile:@"/Users/support/Pictures/cat.JPG"] autorelease];
NSSize size = img.size;
NSBezierPath *path = [NSBezierPath bezierPath];
[[NSColor redColor] setStroke];
[path moveToPoint:NSMakePoint(0.0, 0.0)];
[path lineToPoint:NSMakePoint(size.width, size.height)];
[path moveToPoint:NSMakePoint(0.0, size.height)];
[path lineToPoint:NSMakePoint(size.width, 0.0)];
[path setLineWidth:1];
[path stroke];
[img unlockFocus];
[imageView setImage:img];
...
这应该可以工作,除了线将是2个物理像素宽(当然,与常规屏幕上的图像宽度相似)。试试这个更简单的特殊情况来解决这个问题:
[path setLineWidth:(img.scale > 1) ? 0.5 : 1.0];