react-native-vision-camera/ios/Skia Render Layer/SkImageHelpers.mm

//
//  CMSampleBuffer+toSkImage.m
//  VisionCamera
//
//  Created by Marc Rousavy on 23.11.22.
//  Copyright © 2022 mrousavy. All rights reserved.
//

#import "SkImageHelpers.h"
#import <AVFoundation/AVFoundation.h>
#import <Metal/Metal.h>

#import <include/core/SkColorSpace.h>
#import <include/core/SkSurface.h>
#import <include/core/SkCanvas.h>
#import <include/core/SkData.h>
#import <include/gpu/GrRecordingContext.h>

#include <TargetConditionals.h>
#if TARGET_RT_BIG_ENDIAN
#   define FourCC2Str(fourcc) (const char[]){*((char*)&fourcc), *(((char*)&fourcc)+1), *(((char*)&fourcc)+2), *(((char*)&fourcc)+3),0}
#else
#   define FourCC2Str(fourcc) (const char[]){*(((char*)&fourcc)+3), *(((char*)&fourcc)+2), *(((char*)&fourcc)+1), *(((char*)&fourcc)+0),0}
#endif

CVMetalTextureCacheRef getTextureCache(GrRecordingContext* context) {
  static CVMetalTextureCacheRef textureCache = nil;
  if (textureCache == nil) {
    // Create a new Texture Cache
     auto result = CVMetalTextureCacheCreate(kCFAllocatorDefault,
                                             nil,
                                             MTLCreateSystemDefaultDevice(),
                                             nil,
                                             &textureCache);
     if (result != kCVReturnSuccess || textureCache == nil) {
       throw std::runtime_error("Failed to create Metal Texture Cache!");
     }
  }
  return textureCache;
}

sk_sp<SkImage> SkImageHelpers::convertCMSampleBufferToSkImage(GrRecordingContext* context, CMSampleBufferRef sampleBuffer) {
  auto pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
  double width = CVPixelBufferGetWidth(pixelBuffer);
  double height = CVPixelBufferGetHeight(pixelBuffer);

  // Make sure the format is RGB (BGRA_8888)
  auto format = CVPixelBufferGetPixelFormatType(pixelBuffer);
  if (format != kCVPixelFormatType_32BGRA) {
    auto fourCharCode = @(FourCC2Str(format));
    auto error = std::string("VisionCamera: Frame has unknown Pixel Format (") + fourCharCode.UTF8String + std::string(") - cannot convert to SkImage!");
    throw std::runtime_error(error);
  }
  
  auto textureCache = getTextureCache(context);

  // Convert CMSampleBuffer* -> CVMetalTexture*
  CVMetalTextureRef cvTexture;
  CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault,
                                           textureCache,
                                           pixelBuffer,
                                           nil,
                                           MTLPixelFormatBGRA8Unorm,
                                           width,
                                           height,
                                           0, // plane index
                                           &cvTexture);
  GrMtlTextureInfo textureInfo;
  auto mtlTexture = CVMetalTextureGetTexture(cvTexture);
  textureInfo.fTexture.retain((__bridge void*)mtlTexture);

  // Wrap it in a GrBackendTexture
  GrBackendTexture texture(width, height, GrMipmapped::kNo, textureInfo);

  // Create an SkImage from the existing texture
  auto image = SkImage::MakeFromTexture(context,
                                        texture,
                                        kTopLeft_GrSurfaceOrigin,
                                        kBGRA_8888_SkColorType,
                                        kOpaque_SkAlphaType,
                                        SkColorSpace::MakeSRGB());

  // Release the Texture wrapper (it will still be strong)
  CFRelease(cvTexture);

  return image;
}

SkRect SkImageHelpers::createCenterCropRect(SkRect sourceRect, SkRect destinationRect) {
  SkSize src;
  if (destinationRect.width() / destinationRect.height() > sourceRect.width() / sourceRect.height()) {
    src = SkSize::Make(sourceRect.width(), (sourceRect.width() * destinationRect.height()) / destinationRect.width());
  } else {
    src = SkSize::Make((sourceRect.height() * destinationRect.width()) / destinationRect.height(), sourceRect.height());
  }

  return inscribe(src, sourceRect);
}

SkRect SkImageHelpers::inscribe(SkSize size, SkRect rect) {
  auto halfWidthDelta = (rect.width() - size.width()) / 2.0;
  auto halfHeightDelta = (rect.height() - size.height()) / 2.0;
  return SkRect::MakeXYWH(rect.x() + halfWidthDelta,
                          rect.y() + halfHeightDelta,
                          size.width(),
                          size.height());
}