这就是我现在所拥有的：

precision mediump float;

varying highp vec2 textureCoordinate;
varying highp vec2 textureCoordinate2;
uniform sampler2D inputImageTexture;
uniform sampler2D inputImageTexture2;
uniform float inputImageTextureWidth;
uniform float inputImageTextureHeight;

#define PI 3.14159265

float width = inputImageTextureWidth; //texture width
float height = inputImageTextureHeight; //texture height

vec2 texel = vec2(1.0/width,1.0/height);

//uniform variables from external script

uniform float focalDepth;  //focal distance value in meters,but you may use autofocus option below
uniform float focalLength; //focal length in mm
uniform float fstop; //f-stop value
bool showFocus = false; //show debug focus point and focal range (red = focal point,green = focal range)

float znear = 0.1; //camera clipping start
float zfar = 5.0; //camera clipping end

//------------------------------------------
//user variables

int samples = 3; //samples on the first ring
int rings = 3; //ring count

bool manualdof = false; //manual dof calculation
float ndofstart = 1.0; //near dof blur start
float ndofdist = 2.0; //near dof blur falloff distance
float fdofstart = 1.0; //far dof blur start
float fdofdist = 3.0; //far dof blur falloff distance

float CoC = 0.03;//circle of confusion size in mm (35mm film = 0.03mm)

bool vignetting = false; //use optical lens vignetting?
float vignout = 1.3; //vignetting outer border
float vignin = 0.0; //vignetting inner border
float vignfade = 22.0; //f-stops till vignete fades

bool autofocus = false; //use autofocus in shader? disable if you use external focalDepth value
vec2 focus = vec2(0.5,0.5); // autofocus point on screen (0.0,0.0 - left lower corner,1.0,1.0 - upper right)
float maxblur = 1.0; //clamp value of max blur (0.0 = no blur,1.0 default)

float threshold = 0.5; //highlight threshold;
float gain = 2.0; //highlight gain;

float bias = 0.5; //bokeh edge bias
float fringe = 0.7; //bokeh chromatic aberration/fringing

bool noise = false; //use noise instead of pattern for sample dithering
float namount = 0.0001; //dither amount

bool depthblur = false; //blur the depth buffer?
float dbsize = 1.25; //depthblursize

/*
 next part is experimental
 not looking good with small sample and ring count
 looks okay starting from samples = 4,rings = 4
 */

bool pentagon = false; //use pentagon as bokeh shape?
float feather = 0.4; //pentagon shape feather

//------------------------------------------


float penta(vec2 coords) //pentagonal shape
{
    float scale = float(rings) - 1.3;
    vec4  HS0 = vec4( 1.0,0.0,1.0);
    vec4  HS1 = vec4( 0.309016994,0.951056516,1.0);
    vec4  HS2 = vec4(-0.809016994,0.587785252,1.0);
    vec4  HS3 = vec4(-0.809016994,-0.587785252,1.0);
    vec4  HS4 = vec4( 0.309016994,-0.951056516,1.0);
    vec4  HS5 = vec4( 0.0,1.0);

    vec4  one = vec4( 1.0 );

    vec4 P = vec4((coords),vec2(scale,scale));

    vec4 dist = vec4(0.0);
    float inorout = -4.0;

    dist.x = dot( P,HS0 );
    dist.y = dot( P,HS1 );
    dist.z = dot( P,HS2 );
    dist.w = dot( P,HS3 );

    dist = smoothstep( -feather,feather,dist );

    inorout += dot( dist,one );

    dist.x = dot( P,HS4 );
    dist.y = HS5.w - abs( P.z );

    dist = smoothstep( -feather,dist );
    inorout += dist.x;

    return clamp( inorout,1.0 );
}

float bdepth(vec2 coords) //blurring depth
{
    float d = 0.0;
    float kernel[9];
    vec2 offset[9];

    vec2 wh = vec2(texel.x,texel.y) * dbsize;

    offset[0] = vec2(-wh.x,-wh.y);
    offset[1] = vec2( 0.0,-wh.y);
    offset[2] = vec2( wh.x -wh.y);

    offset[3] = vec2(-wh.x,0.0);
    offset[4] = vec2( 0.0,0.0);
    offset[5] = vec2( wh.x,0.0);

    offset[6] = vec2(-wh.x,wh.y);
    offset[7] = vec2( 0.0,wh.y);
    offset[8] = vec2( wh.x,wh.y);

    kernel[0] = 1.0/16.0;   kernel[1] = 2.0/16.0;   kernel[2] = 1.0/16.0;
    kernel[3] = 2.0/16.0;   kernel[4] = 4.0/16.0;   kernel[5] = 2.0/16.0;
    kernel[6] = 1.0/16.0;   kernel[7] = 2.0/16.0;   kernel[8] = 1.0/16.0;


    for( int i=0; i<9; i++ )
    {
        float tmp = texture2D(inputImageTexture2,coords + offset[i]).r;
        d += tmp * kernel[i];
    }

    return d;
}


vec3 color(vec2 coords,float blur) //processing the sample
{
    vec3 col = vec3(0.0);

    col.r = texture2D(inputImageTexture,coords + vec2(0.0,1.0)*texel*fringe*blur).r;
    col.g = texture2D(inputImageTexture,coords + vec2(-0.866,-0.5)*texel*fringe*blur).g;
    col.b = texture2D(inputImageTexture,coords + vec2(0.866,-0.5)*texel*fringe*blur).b;

    vec3 lumcoeff = vec3(0.299,0.587,0.114);
    float lum = dot(col.rgb,lumcoeff);
    float thresh = max((lum-threshold)*gain,0.0);
    return col+mix(vec3(0.0),col,thresh*blur);
}

vec2 rand(vec2 coord) //generating noise/pattern texture for dithering
{
    float noiseX = ((fract(1.0-coord.s*(width/2.0))*0.25)+(fract(coord.t*(height/2.0))*0.75))*2.0-1.0;
    float noiseY = ((fract(1.0-coord.s*(width/2.0))*0.75)+(fract(coord.t*(height/2.0))*0.25))*2.0-1.0;

    if (noise)
    {
        noiseX = clamp(fract(sin(dot(coord,vec2(12.9898,78.233))) * 43758.5453),1.0)*2.0-1.0;
        noiseY = clamp(fract(sin(dot(coord,78.233)*2.0)) * 43758.5453),1.0)*2.0-1.0;
    }
    return vec2(noiseX,noiseY);
}

vec3 debugFocus(vec3 col,float blur,float depth)
{
    float edge = 0.002*depth; //distance based edge smoothing
    float m = clamp(smoothstep(0.0,edge,blur),1.0);
    float e = clamp(smoothstep(1.0-edge,1.0);

    col = mix(col,vec3(1.0,0.0),(1.0-m)*0.6);
    col = mix(col,vec3(0.0,1.0),((1.0-e)-(1.0-m))*0.2);

    return col;
}

float linearize(float depth)
{
    return -zfar * znear / (depth * (zfar - znear) - zfar);
}

float vignette()
{
    float dist = distance(textureCoordinate.xy,vec2(0.5,0.5));
    dist = smoothstep(vignout+(fstop/vignfade),vignin+(fstop/vignfade),dist);
    return clamp(dist,1.0);
}

void main()
{
    //scene depth calculation

    float depth = linearize(texture2D(inputImageTexture2,textureCoordinate2.xy).x);

    if (depthblur)
    {
        depth = linearize(bdepth(textureCoordinate2.xy));
    }

    //focal plane calculation

    float fDepth = focalDepth;

    if (autofocus)
    {
        fDepth = linearize(texture2D(inputImageTexture2,focus).x);
    }

    //dof blur factor calculation

    float blur = 0.0;

    if (manualdof)
    {
        float a = depth-fDepth; //focal plane
        float b = (a-fdofstart)/fdofdist; //far DoF
        float c = (-a-ndofstart)/ndofdist; //near Dof
        blur = (a>0.0)?b:c;
    }

    else
    {
        float f = focalLength; //focal length in mm
        float d = fDepth*1000.0; //focal plane in mm
        float o = depth*1000.0; //depth in mm

        float a = (o*f)/(o-f);
        float b = (d*f)/(d-f);
        float c = (d-f)/(d*fstop*CoC);

        blur = abs(a-b)*c;
    }

    blur = clamp(blur,1.0);

    // calculation of pattern for ditering

    vec2 noise = rand(textureCoordinate.xy)*namount*blur;

    // getting blur x and y step factor

    float w = (1.0/width)*blur*maxblur+noise.x;
    float h = (1.0/height)*blur*maxblur+noise.y;

    // calculation of final color

    vec3 col = vec3(0.0);

    if(blur < 0.05) //some optimization thingy
    {
        col = texture2D(inputImageTexture,textureCoordinate.xy).rgb;
    }

    else
    {
        col = texture2D(inputImageTexture,textureCoordinate.xy).rgb;
        float s = 1.0;
        int ringsamples;

        for (int i = 1; i <= rings; i += 1)
        {
            ringsamples = i * samples;

            for (int j = 0 ; j < ringsamples ; j += 1)
            {
                float step = PI*2.0 / float(ringsamples);
                float pw = (cos(float(j)*step)*float(i));
                float ph = (sin(float(j)*step)*float(i));
                float p = 1.0;
                if (pentagon)
                {
                    p = penta(vec2(pw,ph));
                }
                col += color(textureCoordinate.xy + vec2(pw*w,ph*h),blur)*mix(1.0,(float(i))/(float(rings)),bias)*p;
                s += 1.0*mix(1.0,bias)*p;
            }
        }
        col /= s; //divide by sample count
    }

    if (showFocus)
    {
        col = debugFocus(col,blur,depth);
    }

    if (vignetting)
    {
        col *= vignette();
    }

    gl_FragColor.rgb = col;
    gl_FragColor.a = 1.0;
}

这是我的散景过滤器,GPUImageTwoInputFilter的子类：

@implementation GPUImageBokehFilter

- (id)init;
{
    NSString *fragmentShaderPathname = [[NSBundle mainBundle] pathForResource:@"BokehShader" ofType:@"fsh"];
    NSString *fragmentShaderString = [NSString stringWithContentsOfFile:fragmentShaderPathname encoding:NSUTF8StringEncoding error:nil];

    if (!(self = [super initWithFragmentShaderFromString:fragmentShaderString]))
    {
        return nil;
    }

    focalDepthUniform = [filterProgram uniformIndex:@"focalDepth"];
    focalLengthUniform = [filterProgram uniformIndex:@"focalLength"];
    fStopUniform = [filterProgram uniformIndex:@"fstop"];

    [self setFocalDepth:1.0];
    [self setFocalLength:35.0];
    [self setFStop:2.2];

    return self;
}


#pragma mark -
#pragma mark Accessors

- (void)setFocalDepth:(float)focalDepth {
    _focalDepth = focalDepth;
    [self setFloat:_focalDepth forUniform:focalDepthUniform program:filterProgram];
}

- (void)setFocalLength:(float)focalLength {
    _focalLength = focalLength;
    [self setFloat:_focalLength forUniform:focalLengthUniform program:filterProgram];
}

- (void)setFStop:(CGFloat)fStop {
    _fStop = fStop;
    [self setFloat:_fStop forUniform:fStopUniform program:filterProgram];
}

@end

最后,这是我使用所述过滤器的方式：

@implementation ViewController {
    GPUImageBokehFilter *bokehFilter;
    GPUImagePicture *bokehMap;
    UIImage *inputImage;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    inputImage = [UIImage imageNamed:@"stones"];
    bokehMap = [[GPUImagePicture alloc] initWithImage:[UIImage imageNamed:@"bokehmask"]];
    _backgroundImage.image = inputImage;

    bokehFilter = [[GPUImageBokehFilter alloc] init];

    [self processImage];
}
- (IBAction)dataInputUpdated:(id)sender {
    [self processImage];
}
- (void *)processImage {
    dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT,0),^{
        GPUImagePicture *gpuPicture = [[GPUImagePicture alloc] initWithImage:inputImage];
        [gpuPicture addTarget:bokehFilter];
        [gpuPicture processImage];
        [bokehMap addTarget:bokehFilter];
        [bokehMap processImage];
        [bokehFilter useNextFrameForImageCapture];
        [bokehFilter setFloat:inputImage.size.width forUniformName:@"inputImageTextureWidth"];
        [bokehFilter setFloat:inputImage.size.height forUniformName:@"inputImageTextureHeight"];

        UIImage *blurredImage = [bokehFilter imageFromCurrentFramebuffer];
        dispatch_async(dispatch_get_main_queue(),^{
            [self displayNewImage:blurredImage];
        });
    });
}
- (void)displayNewImage:(UIImage*)newImage {
    [UIView transitionWithView:_backgroundImage
                      duration:.6f
                       options:UIViewAnimationOptionTransitionCrossDissolve
                    animations:^{
                        _backgroundImage.image = newImage;
                    } completion:nil];
}

...

第一个图像是我试图模糊的图像,第二个图像是一个随机渐变来测试着色器的深度图：

当我在iPhone上启动应用程序时,我得到了这个：

移动滑块(触发dataInputChanged方法)后,我得到：

虽然这看起来比第一张图片要好得多,但我仍有一些问题：

>有一条对角线的嘈杂线(在我放在图片上的红线内)似乎没有模糊.
>图像的左上角是模糊的,即使它不应该是模糊的.

为什么我会得到这种奇怪的行为？着色器输出不应该每次都相同吗？
另外,我如何让它尊重深度图？我的GLSL着色器知识非常有限,所以请耐心等待.