从 AdobeLabsUXMagicSelectionView (Adobe Creative SDK) 获取前景
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【中文标题】从 AdobeLabsUXMagicSelectionView (Adobe Creative SDK) 获取前景【英文标题】:Get foreground from AdobeLabsUXMagicSelectionView (Adobe Creative SDK) 【发布时间】:2016-01-27 16:55:39 【问题描述】:我正在尝试使用AdobeLabsUXMagicSelectionView,但遇到了两个问题。我想使用这两种方法“剪切”选定区域(前景):
方法 1) getForeground:andMatte:
它没有给我正确的前景。当我选择一个区域并调用getForeground:andMatte
时,我给了我前景和背景(混合)。
选择狗的脸
割狗的脸
文档说:
或者,如果您不需要处理底层位图 直接,并打算将结果用作 CoreGraphics 的输入或 CoreImage,你可以调用:
方法 2)在此之后,我尝试像文档一样“剪切”
extension AdobeLabsUXMagicSelectionView
func foregroundCGImage() -> CGImage
let w = size_t(self.image.size.width)
let h = size_t(self.image.size.height)
let data = UnsafeMutablePointer<UInt8>(malloc(4 * w * h * sizeof(UInt8)))
self.readForegroundAndMatteIntoBuffer(data)
for var i = 0; i < 4 * w * h; i += 4
let alpha: UInt8 = UInt8(data[i + 3]) / 255
data[i] *= alpha
data[i + 1] *= alpha
data[i + 2] *= alpha
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.NoneSkipLast.rawValue)
let ctx = CGBitmapContextCreate(data, w, h, 8, 4 * w, CGColorSpaceCreateDeviceRGB(), bitmapInfo.rawValue)
let imageRef = CGBitmapContextCreateImage(ctx)!
return imageRef
但它只绘制(黑色)图像的未选择部分(背景)。
有人可以帮忙吗?我想要的是获得选定区域的最终图像。
更新:
正如@DonWoodward 所说,我已经创建了这个类别:
@implementation AdobeLabsUXMagicSelectionView (Foreground)
- (UIImage *)getForeground
// show the results
// first create a UIImage of just the foreground bits per the documentation in AdobeLabsUXMagicSelectionView.h
size_t w = self.image.size.width;
size_t h = self.image.size.height;
uint8_t *data = (uint8_t *)malloc(4*w*h*sizeof(uint8_t));
[self readForegroundAndMatteIntoBuffer:data];
// Paint the non-selected portion of the image black
for (int i = 0; i < 4*w*h; i += 4)
float alpha = (float)data[i + 3] / 255;
data[i ] *= alpha;
data[i + 1] *= alpha;
data[i + 2] *= alpha;
CGContextRef ctx = CGBitmapContextCreate(data, w, h, 8, 4*w, CGColorSpaceCreateDeviceRGB(), (CGBitmapInfo)kCGImageAlphaNoneSkipLast);
CGImageRef imageRef = CGBitmapContextCreateImage(ctx);
UIImage * foregroundBits = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return foregroundBits;
@end
但结果在“前景”周围有很多黑色像素。
我需要什么?获得一个“干净”的前景(没有黑色像素的选定区域)放在 UIImageView 上
【问题讨论】:
【参考方案1】:我认为问题在于您的比例因子是uint8_t
类型,因此您将比例因子剪裁为零。让它成为一个浮动,它应该工作。这是来自 MagicPuppy(在目标 c 中)的代码:
// show the results
// first create a UIImage of just the foreground bits per the documentation in AdobeLabsUXMagicSelectionView.h
size_t w = _magicSelectionView.image.size.width;
size_t h = _magicSelectionView.image.size.height;
uint8_t *data = (uint8_t *)malloc(4*w*h*sizeof(uint8_t));
[_magicSelectionView readForegroundAndMatteIntoBuffer:data];
// Paint the non-selected portion of the image black
for (int i = 0; i < 4*w*h; i += 4)
float alpha = (float)data[i + 3] / 255;
data[i ] *= alpha;
data[i + 1] *= alpha;
data[i + 2] *= alpha;
CGContextRef ctx = CGBitmapContextCreate(data, w, h, 8, 4*w, CGColorSpaceCreateDeviceRGB(), (CGBitmapInfo)kCGImageAlphaNoneSkipLast);
CGImageRef imageRef = CGBitmapContextCreateImage(ctx);
UIImage * foregroundBits = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
// show the results
_resultsView = [[UIImageView alloc] initWithFrame: CGRectMake(0, VIEW_Y_OFFSET, self.view.bounds.size.width, self.view.bounds.size.height-VIEW_Y_OFFSET)];
_resultsView.contentMode = UIViewContentModeScaleAspectFit;
[_resultsView setImage: foregroundBits];
[self.view addSubview: _resultsView];
【讨论】:
【参考方案2】:在这种情况下,您将 RGB 通道与 Alpha 通道进行预乘,这意味着您在创建上下文时需要使用 kCGImageAlphaPremultipliedLast
,如下所示:
// Paint the non-selected portion of the image black
for (int i = 0; i < 4*w*h; i += 4)
float alpha = (float)data[i + 3] / 255;
data[i ] *= alpha;
data[i + 1] *= alpha;
data[i + 2] *= alpha;
CGContextRef ctx = CGBitmapContextCreate(data, w, h, 8, 4*w, CGColorSpaceCreateDeviceRGB(), (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
CGImageRef imageRef = CGBitmapContextCreateImage(ctx);
UIImage * foregroundBits = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
更多信息可以在CGImage docs找到
另外,您也可以尝试使用 CGImageCreateWithMask
与
- (void)getForeground:(UIImage **)foregroundImage andMatte:(UIImage **)matteImage
如Quartz 2D Programming Guide中所述
UIImage *fg;
UIImage *matte;
[_magicSelectionView getForeground:&fg andMatte:&matte];
CGImageRef mattedForeground = CGImageCreateWithMask(fg.CGImage, matte.CGImage);
UIImage *foregroundBits = [UIImage imageWithCGImage:mattedForeground];
// show the results
_resultsView = [[UIImageView alloc] initWithFrame: CGRectMake(0, VIEW_Y_OFFSET, self.view.bounds.size.width, self.view.bounds.size.height-VIEW_Y_OFFSET)];
_resultsView.contentMode = UIViewContentModeScaleAspectFit;
[_resultsView setImage: foregroundBits];
[self.view addSubview: _resultsView];
如果这些都不起作用,则用于呈现结果的UIImageViews
的配置可能存在一些问题,但如果没有该代码,就很难说。
【讨论】:
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