从具有核心图像的查找图像中筛选图像

这个答案的所有功劳都归Nghia Tran所有。如果你看到这个,谢谢!

结果,一直以来只有一个答案。Nghia Tran写了一篇文章 here 他解决了我确切的用例。

他很乐意提供一个扩展来生成 CIFilter 从一个查找图像,我将粘贴到下面,为将来的开发人员保留这个答案。

您需要导入 CIFilter+LUT.h 如果你用的是斯威夫特。

下面是一个演示如何在GPU上使用它的片段 斯威夫特4 .这离优化还很远,应该缓存上下文等,但这是一个很好的起点。

static func applyFilter(with lookupImage: UIImage, to image: UIImage) -> UIImage? {
    guard let cgInputImage = image.cgImage else {
        return nil
    }

    guard let glContext = EAGLContext(api: .openGLES2) else {
        return nil
    }

    let ciContext = CIContext(eaglContext: glContext)

    guard let lookupFilter = CIFilter(lookupImage: lookupImage, dimension: 64) else {
        return nil
    }

    lookupFilter.setValue(CIImage(cgImage: cgInputImage),
                          forKey: "inputImage")

    guard let output = lookupFilter.outputImage else {
        return nil
    }

    guard let cgOutputImage = ciContext.createCGImage(output, from: output.extent) else {
        return nil
    }

    return UIImage(cgImage: cgOutputImage)
}

cifilter+lut.h过滤

#import <CoreImage/CoreImage.h>
@import UIKit.UIImage;

@class CIFilter;

@interface CIFilter (LUT)
+(CIFilter *) filterWithLookupImage:(UIImage *)image dimension:(NSInteger) n;
@end

C滤波器+LUT.M

#import "CIFilter+LUT.h"
#import <CoreImage/CoreImage.h>
#import <OpenGLES/EAGL.h>

@implementation CIFilter (LUT)

+(CIFilter *)filterWithLookupImage:(UIImage *)image dimension:(NSInteger)n {
    NSInteger width = CGImageGetWidth(image.CGImage);
    NSInteger height = CGImageGetHeight(image.CGImage);
    NSInteger rowNum = height / n;
    NSInteger columnNum = width / n;

    if ((width % n != 0) || (height % n != 0) || (rowNum * columnNum != n)) {
        NSLog(@"Invalid colorLUT");
        return nil;
    }

    unsigned char *bitmap = [self createRGBABitmapFromImage:image.CGImage];

    if (bitmap == NULL) {
        return nil;
    }

    NSInteger size = n * n * n * sizeof(float) * 4;
    float *data = malloc(size);
    int bitmapOffest = 0;
    int z = 0;

    for (int row = 0; row <  rowNum; row++) {
        for (int y = 0; y < n; y++) {
            int tmp = z;
            for (int col = 0; col < columnNum; col++) {
                for (int x = 0; x < n; x++) {
                    float r = (unsigned int)bitmap[bitmapOffest];
                    float g = (unsigned int)bitmap[bitmapOffest + 1];
                    float b = (unsigned int)bitmap[bitmapOffest + 2];
                    float a = (unsigned int)bitmap[bitmapOffest + 3];

                    NSInteger dataOffset = (z*n*n + y*n + x) * 4;

                    data[dataOffset] = r / 255.0;
                    data[dataOffset + 1] = g / 255.0;
                    data[dataOffset + 2] = b / 255.0;
                    data[dataOffset + 3] = a / 255.0;

                    bitmapOffest += 4;
                }
                z++;
            }
            z = tmp;
        }
        z += columnNum;
    }

    free(bitmap);

    CIFilter *filter = [CIFilter filterWithName:@"CIColorCube"];
    [filter setValue:[NSData dataWithBytesNoCopy:data length:size freeWhenDone:YES] forKey:@"inputCubeData"];
    [filter setValue:[NSNumber numberWithInteger:n] forKey:@"inputCubeDimension"];

    return filter;
}

+ (unsigned char *)createRGBABitmapFromImage:(CGImageRef)image {
    CGContextRef context = NULL;
    CGColorSpaceRef colorSpace;
    unsigned char *bitmap;
    NSInteger bitmapSize;
    NSInteger bytesPerRow;

    size_t width = CGImageGetWidth(image);
    size_t height = CGImageGetHeight(image);

    bytesPerRow = (width * 4);
    bitmapSize = (bytesPerRow * height);

    bitmap = malloc(bitmapSize);
    if (bitmap == NULL) {
        return NULL;
    }

    colorSpace = CGColorSpaceCreateDeviceRGB();
    if (colorSpace == NULL) {
        free(bitmap);
        return NULL;
    }

    context = CGBitmapContextCreate (bitmap, width,  height, 8, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast);
    CGColorSpaceRelease(colorSpace);

    if (context == NULL) {
        free (bitmap);
    }

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), image);
    CGContextRelease(context);

    return bitmap;
}
@end