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];

}