NSString *const kFWLomofiShaderString = SHADER_STRING( precision lowp float;  varying highp vec2 textureCoordinate;  uniform sampler2D inputImageTexture; uniform sampler2D inputImageTexture2; uniform sampler2D inputImageTexture3;  void main() {          vec3 texel = texture2D(inputImageTexture, textureCoordinate).rgb;//获取要处理图像的rgb值向量          vec2 red = vec2(texel.r, 0.16666);     vec2 green = vec2(texel.g, 0.5);     vec2 blue = vec2(texel.b, 0.83333);//使要处理的图像和柔光混合，生成新的像素          texel.rgb = vec3(                      texture2D(inputImageTexture2, red).r,                      texture2D(inputImageTexture2, green).g,                      texture2D(inputImageTexture2, blue).b);//前面生成新的像素再与第二个输入图像的像素进行混合     //使用第三个图像作为暗角模板与前面的像素混合     vec2 tc = (2.0 * textureCoordinate) - 1.0;     float d = dot(tc, tc);     vec2 lookup = vec2(d, texel.r);     texel.r = texture2D(inputImageTexture3, lookup).r;     lookup.y = texel.g;     texel.g = texture2D(inputImageTexture3, lookup).g;     lookup.y = texel.b;     texel.b    = texture2D(inputImageTexture3, lookup).b;

//生成最终的LOMO效果

gl_FragColor = vec4(texel,1.0); } );

@implementation FWLomofiFilter- (id)init{    if (!(self = [super init]))    {        return nil;    }        FWFilter6 *filter = [[FWFilter6 alloc] init];    [self addFilter:filter];//设置第二个输入图像    UIImage *image = [UIImage imageNamed:@"lomoMap"];    imageSource1 = [[GPUImagePicture alloc] initWithImage:image];    [imageSource1 addTarget:filter atTextureLocation:1];    [imageSource1 processImage];

//设置第三个输入图像

UIImage *image1 = [UIImage imageNamed:@"vignetteMap"]; imageSource2 = [[GPUImagePicture alloc] initWithImage:image1]; [imageSource2 addTarget:filter atTextureLocation:2]; [imageSource2 processImage]; self.initialFilters = [NSArray arrayWithObjects:filter, nil]; self.terminalFilter = filter; return self; }

+ (UIImage *)applyLomofiFilter:(UIImage *)image

{

    FWLomofiFilter *filter = [[FWLomofiFilter alloc] init];

    [filter forceProcessingAtSize:image.size];

//第一个输入图像

   GPUImagePicture *pic = [[GPUImagePicture alloc] initWithImage:image];

    [pic addTarget:filter];

    [pic processImage];

    [filter useNextFrameForImageCapture];

//得到效果图

    return [filter imageFromCurrentFramebuffer];

}