How to maintain the aspect ratio when using GPUImage?

问题

I found the Instagram has a camera window like 300*300？ its a square, then Im trying to use the GPUImage to make the same camera size.so I wrote like this:

primaryView = [GPUImageView alloc] initWithFrame:
                                   CGRectMake(0,0,300,300)];//define a square view

//define a still camera
stillCamera = [[GPUImageStillCamera alloc]
              initWithSessionPreset:AVCaptureSessionPreset640x480
              cameraPosition:AVCaptureDevicePositionFront];

//make it portrait
stillCamera.outputImageOrientation = UIInterfaceOrientationPortrait;

//define a filter
filter = [[GPUImageFilter alloc] init];

//force the output to 300*300
[filter forceProcessingAtSize:((GPUImageView*)self.primaryView).sizeInPixels];

//set things up
[stillCamera addTarget: filter];
[filter addTarget: primaryView];
[stillCamera startCameraCapture];

Now I really get a square view..but the view looks so flat, its completely distortion, I think it might be something wrong with the aspect ratio.then I set the fill mode of the primary view like this:

[primaryView setFillMode:kGPUImageFillModePreserveAspectRatioAndFill];

then this:

[primaryView setFillMode:kGPUImageFillModePreserveAspectRatio];

then this:

[primaryView kGPUImageFillModeStretch];

FINALLY! none of these work..so what I am missing, any one, help.

回答1:

-forceProcessingAtSize: causes that filter to output an image of exactly the size you provide, ignoring aspect ratio. That squishes your image into a 300x300 square.

If you want to preserve the aspect ratio of your image, you'd want to use -forceProcessingAtSizeRespectingAspectRatio:.

However, that will letterbox your image. To replicate what Instagram does, you probably want to instead cut a square region out of the center of the image. For that, use a crop filter with a square aspect ratio.

来源：https://stackoverflow.com/questions/17783357/how-to-maintain-the-aspect-ratio-when-using-gpuimage

标签

aspect-ratio

gpuimage