使用像素数据创建CVPixelBuffer,但最终图像失真

Question

我通过OpenGLES方法(glReadPixels)或其他方式获取像素,然后创建CVPixelBuffer(带或不带CGImage)进行视频录制,但最终图片失真.当我在iPhone 5c,5s和6上测试时,会在iPhone6上发生这种情况.

看起来像:

这是代码:

CGSize viewSize=self.glView.bounds.size;
NSInteger myDataLength = viewSize.width * viewSize.height * 4;

// allocate array and read pixels into it.
GLubyte *buffer = (GLubyte *) malloc(myDataLength);
glReadPixels(0, 0, viewSize.width, viewSize.height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

// gl renders "upside down" so swap top to bottom into new array.
// there's gotta be a better way, but this works.
GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);
for(int y = 0; y < viewSize.height; y++)
{
    for(int x = 0; x < viewSize.width* 4; x++)
    {
        buffer2[(int)((viewSize.height-1 - y) * viewSize.width * 4 + x)] = buffer[(int)(y * 4 * viewSize.width + x)];
    }
}

free(buffer);

// make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);

// prep the ingredients
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * viewSize.width;
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

// make the cgimage
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGImageRef imageRef = CGImageCreate(viewSize.width , viewSize.height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);

//UIImage *photo = [UIImage imageWithCGImage:imageRef];

int width = CGImageGetWidth(imageRef);
int height = CGImageGetHeight(imageRef);

CVPixelBufferRef pixelBuffer = NULL;
CVReturn status = CVPixelBufferPoolCreatePixelBuffer(NULL, _recorder.pixelBufferAdaptor.pixelBufferPool, &pixelBuffer);

NSAssert((status == kCVReturnSuccess && pixelBuffer != NULL), @"create pixel buffer failed.");

CVPixelBufferLockBaseAddress(pixelBuffer, 0);
void *pxdata = CVPixelBufferGetBaseAddress(pixelBuffer);
NSParameterAssert(pxdata != NULL);//CGContextRef
CGContextRef context = CGBitmapContextCreate(pxdata,
                                             width,
                                             height,
                                             CGImageGetBitsPerComponent(imageRef),
                                             CGImageGetBytesPerRow(imageRef),
                                             colorSpaceRef,
                                             kCGImageAlphaPremultipliedLast);
NSParameterAssert(context);

CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);

CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);

CGColorSpaceRelease(colorSpaceRef);
CGContextRelease(context);
CGImageRelease(imageRef);

free(buffer2);

//CIImage *image = [CIImage imageWithCVPixelBuffer:pixelBuffer];

// ...

CVPixelBufferRelease(pixelBuffer);

Answer 1

注意 - 这个答案涉及图像的整体问题，而不是特定的代码。

这类问题通常是“步幅”，与用于保存图像的内存布局有关，其中每行像素没有紧密地包装在一起

作为示例，源图像可能是 240 像素宽。CMPixelBuffer 可以为每行分配 320 个像素，其中前 240 个像素保存图像，额外的 80 个像素用于填充。在本例中，宽度为 240 像素，步长为 320 像素。

跨步通常意味着您必须在循环中复制每一行像素