我在从CVPixelBuffer获取UIIMage时遇到一些问题。这就是我想要的：
CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(imageDataSampleBuffer);
CFDictionaryRef attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, imageDataSampleBuffer, kCMAttachmentMode_ShouldPropagate);
CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer options:(NSDictionary *)attachments];
if (attachments)
CFRelease(attachments);
size_t width = CVPixelBufferGetWidth(pixelBuffer);
size_t height = CVPixelBufferGetHeight(pixelBuffer);
if (width && height) { // test to make sure we have valid dimensions
UIImage *image = [[UIImage alloc] initWithCIImage:ciImage];
UIImageView *lv = [[UIImageView alloc] initWithFrame:self.view.frame];
lv.contentMode = UIViewContentModeScaleAspectFill;
self.lockedView = lv;
[lv release];
self.lockedView.image = image;
[image release];
}
[ciImage release];
height和width都已正确设置为相机的分辨率。 image已创建，但我似乎是黑色的（或者可能是透明的？）。我不太明白问题出在哪里。任何想法都将不胜感激。
答案 0 :(得分：49)
首先，与您的问题没有直接关系的显而易见的事情：AVCaptureVideoPreviewLayer是将视频从任一摄像机传输到独立视图的最便宜方式，如果这是数据来自哪里，那么没有立即修改它的计划。您无需自行推动，预览图层直接连接到AVCaptureSession并自行更新。
我不得不承认对这个核心问题缺乏信心。 CIImage和其他两种类型的图像之间存在语义差异 - CIImage是图像的配方，不一定由像素支持。它可以是“从这里获取像素，像这样变换，应用此过滤器，像这样变换，与其他图像合并，应用此过滤器”。在您选择渲染之前，系统不知道CIImage的外观。它本身并不知道光栅化它的适当界限。
UIImage声称仅包裹CIImage。它不会将其转换为像素。据推测UIImageView应该实现这一目标，但如果是这样，那么我似乎无法找到你提供适当输出矩形的位置。
我成功地躲避了这个问题：
CIImage *ciImage = [CIImage imageWithCVPixelBuffer:pixelBuffer];
CIContext *temporaryContext = [CIContext contextWithOptions:nil];
CGImageRef videoImage = [temporaryContext
createCGImage:ciImage
fromRect:CGRectMake(0, 0,
CVPixelBufferGetWidth(pixelBuffer),
CVPixelBufferGetHeight(pixelBuffer))];
UIImage *uiImage = [UIImage imageWithCGImage:videoImage];
CGImageRelease(videoImage);
提供了指定输出矩形的明显机会。我确信没有使用CGImage作为中间人的路线，所以请不要认为这个解决方案是最佳做法。
答案 1 :(得分：16)
在Swift中尝试这个。
Swift 4.2：
import VideoToolbox
extension UIImage {
public convenience init?(pixelBuffer: CVPixelBuffer) {
var cgImage: CGImage?
VTCreateCGImageFromCVPixelBuffer(pixelBuffer, nil, &cgImage)
if let cgImage = cgImage {
self.init(cgImage: cgImage)
} else {
return nil
}
}
}
斯威夫特5：
import VideoToolbox
extension UIImage {
public convenience init?(pixelBuffer: CVPixelBuffer) {
var cgImage: CGImage?
VTCreateCGImageFromCVPixelBuffer(pixelBuffer, options: nil, imageOut: &cgImage)
if let cgImage = cgImage {
self.init(cgImage: cgImage)
} else {
return nil
}
}
}
注意：这仅适用于RGB像素缓冲区，不适用于灰度级。
答案 2 :(得分：13)
获得UIImage的另一种方法。至少在我的情况下，执行速度快〜10倍：
int w = CVPixelBufferGetWidth(pixelBuffer);
int h = CVPixelBufferGetHeight(pixelBuffer);
int r = CVPixelBufferGetBytesPerRow(pixelBuffer);
int bytesPerPixel = r/w;
unsigned char *buffer = CVPixelBufferGetBaseAddress(pixelBuffer);
UIGraphicsBeginImageContext(CGSizeMake(w, h));
CGContextRef c = UIGraphicsGetCurrentContext();
unsigned char* data = CGBitmapContextGetData(c);
if (data != NULL) {
int maxY = h;
for(int y = 0; y<maxY; y++) {
for(int x = 0; x<w; x++) {
int offset = bytesPerPixel*((w*y)+x);
data[offset] = buffer[offset]; // R
data[offset+1] = buffer[offset+1]; // G
data[offset+2] = buffer[offset+2]; // B
data[offset+3] = buffer[offset+3]; // A
}
}
}
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
答案 3 :(得分：8)
除非您的图像数据采用某种不同的格式，需要调整或转换 - 我建议不要增加任何内容...只需使用memcpy将数据打入上下文内存区域，如下所示：
//not here... unsigned char *buffer = CVPixelBufferGetBaseAddress(pixelBuffer);
UIGraphicsBeginImageContext(CGSizeMake(w, h));
CGContextRef c = UIGraphicsGetCurrentContext();
void *ctxData = CGBitmapContextGetData(c);
// MUST READ-WRITE LOCK THE PIXEL BUFFER!!!!
CVPixelBufferLockBaseAddress(pixelBuffer, 0);
void *pxData = CVPixelBufferGetBaseAddress(pixelBuffer);
memcpy(ctxData, pxData, 4 * w * h);
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
... and so on...
答案 4 :(得分：3)
以前的方法让我有CG Raster Data泄漏。这种转换方法对我没有泄漏：
@autoreleasepool {
CGImageRef cgImage = NULL;
OSStatus res = CreateCGImageFromCVPixelBuffer(pixelBuffer,&cgImage);
if (res == noErr){
UIImage *image= [UIImage imageWithCGImage:cgImage scale:1.0 orientation:UIImageOrientationUp];
}
CGImageRelease(cgImage);
}
static OSStatus CreateCGImageFromCVPixelBuffer(CVPixelBufferRef pixelBuffer, CGImageRef *imageOut)
{
OSStatus err = noErr;
OSType sourcePixelFormat;
size_t width, height, sourceRowBytes;
void *sourceBaseAddr = NULL;
CGBitmapInfo bitmapInfo;
CGColorSpaceRef colorspace = NULL;
CGDataProviderRef provider = NULL;
CGImageRef image = NULL;
sourcePixelFormat = CVPixelBufferGetPixelFormatType( pixelBuffer );
if ( kCVPixelFormatType_32ARGB == sourcePixelFormat )
bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaNoneSkipFirst;
else if ( kCVPixelFormatType_32BGRA == sourcePixelFormat )
bitmapInfo = kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst;
else
return -95014; // only uncompressed pixel formats
sourceRowBytes = CVPixelBufferGetBytesPerRow( pixelBuffer );
width = CVPixelBufferGetWidth( pixelBuffer );
height = CVPixelBufferGetHeight( pixelBuffer );
CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
sourceBaseAddr = CVPixelBufferGetBaseAddress( pixelBuffer );
colorspace = CGColorSpaceCreateDeviceRGB();
CVPixelBufferRetain( pixelBuffer );
provider = CGDataProviderCreateWithData( (void *)pixelBuffer, sourceBaseAddr, sourceRowBytes * height, ReleaseCVPixelBuffer);
image = CGImageCreate(width, height, 8, 32, sourceRowBytes, colorspace, bitmapInfo, provider, NULL, true, kCGRenderingIntentDefault);
if ( err && image ) {
CGImageRelease( image );
image = NULL;
}
if ( provider ) CGDataProviderRelease( provider );
if ( colorspace ) CGColorSpaceRelease( colorspace );
*imageOut = image;
return err;
}
static void ReleaseCVPixelBuffer(void *pixel, const void *data, size_t size)
{
CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)pixel;
CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
CVPixelBufferRelease( pixelBuffer );
}
答案 5 :(得分：0)
一种现代的解决方案是
let image = UIImage(ciImage: CIImage(cvPixelBuffer: YOUR_BUFFER))