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:];

    [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:]; [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];

}