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如何水平移动图像以创建循环效果?

cifilter nsimage cocoa

0

Marek H · 技术社区 · 7 年前

如何水平移动图像,使移动的像素出现在另一侧,使其看起来像一个循环? 目前我正在使用drawInRect。有没有什么更好的方法可以做到这一点?

- (CIImage *)image:(NSImage *)image shiftedBy:(CGFloat)shiftAmount
{

    NSUInteger width = image.size.width;
    NSUInteger height = image.size.height;
    NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
                                                  pixelsWide:width
                                                  pixelsHigh:height
                                               bitsPerSample:8
                                             samplesPerPixel:4
                                                    hasAlpha:YES
                                                    isPlanar:NO
                                              colorSpaceName:NSDeviceRGBColorSpace
                                                 bytesPerRow:0
                                                bitsPerPixel:0];
    [rep setSize:NSMakeSize(width, height)];
    [NSGraphicsContext saveGraphicsState];
    NSGraphicsContext *context = [NSGraphicsContext graphicsContextWithBitmapImageRep:rep];
    [NSGraphicsContext setCurrentContext:context];


    CGRect rect0 = CGRectMake(0, 0, width, height);
    CGRect leftSourceRect, rightSourceRect;
    CGRectDivide(rect0, &leftSourceRect, &rightSourceRect, shiftAmount, CGRectMinXEdge);
    CGRect rightDestinationRect = CGRectOffset(leftSourceRect, width - rightSourceRect.origin.x, 0);
    CGRect leftDestinationRect = rightSourceRect;
    leftDestinationRect.origin.x = 0;

    [image drawInRect:leftDestinationRect fromRect:rightSourceRect operation:NSCompositingOperationSourceOver fraction:1.0];
    [image drawInRect:rightDestinationRect fromRect:leftSourceRect operation:NSCompositingOperationSourceOver fraction:1.0];

    [NSGraphicsContext restoreGraphicsState];
    return [[CIImage alloc] initWithBitmapImageRep:rep];
}

2 回复 | 直到 7 年前

1

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Marek H 7 年前

我尝试使用CIFilter,但是性能下降了3-4倍。但是,代码更具可读性。

- (CIImage *)image:(NSImage *)image shiftXBy:(CGFloat)shiftX YBy:(CGFloat)shiftY
{
    //avoid calling TIFFRepresentation here cause the performance hit is even bigger
    CIImage *ciImage = [[CIImage alloc] initWithData:[image TIFFRepresentation]];
    CGAffineTransform xform = CGAffineTransformIdentity;
    NSValue *xformObj = [NSValue valueWithBytes:&xform objCType:@encode(CGAffineTransform)];
    ciImage = [ciImage imageByApplyingFilter:@"CIAffineTile"
                         withInputParameters:@{kCIInputTransformKey : xformObj} ];
    ciImage = [ciImage imageByCroppingToRect:CGRectMake(shiftX, shiftY, image.size.width, image.size.height)];
    return ciImage;
}

2

0

pointum 7 年前

你的 NSView 子类应该具有 wantsLayer 和 layerUsesCoreImageFilters 着手 true .
将您的图像分配给 content 性质 NSView.layer (或添加新的子层)。
创造 CIAffineTile

现在,您可以更改过滤器的值,而无需重新加载或重画图像。这一切都将是硬件加速的。