ios – GPUImage为每个RGB通道添加色调/颜色调整(调整红色以更加粉红色或橙色)

precision highp float;
 varying highp vec2 textureCoordinate;

 uniform sampler2D inputimageTexture;
 uniform mediump float hueAdjust;
 const highp  vec4  kRGBToYPrime = vec4 (0.299,0.587,0.114,0.0);
 const highp  vec4  kRGBToI     = vec4 (0.595716,-0.274453,-0.321263,0.0);
 const highp  vec4  kRGBToQ     = vec4 (0.211456,-0.522591,0.31135,0.0);

 const highp  vec4  kYIQToR   = vec4 (1.0,0.9563,0.6210,0.0);
 const highp  vec4  kYIQToG   = vec4 (1.0,-0.2721,-0.6474,0.0);
 const highp  vec4  kYIQToB   = vec4 (1.0,-1.1070,1.7046,0.0);

 void main ()
 {
     // Sample the input pixel
     highp vec4 color   = texture2D(inputimageTexture,textureCoordinate);

     // Convert to YIQ
     highp float   YPrime  = dot (color,kRGBToYPrime);
     highp float   I      = dot (color,kRGBToI);
     highp float   Q      = dot (color,kRGBToQ);

     // Calculate the hue and chroma
     highp float   hue     = atan (Q,I);
     highp float   chroma  = sqrt (I * I + Q * Q);

     // Make the user's adjustments
     hue += (-hueAdjust); //why negative rotation?

     // Convert back to YIQ
     Q = chroma * sin (hue);
     I = chroma * cos (hue);

     // Convert back to RGB
     highp vec4    yIQ   = vec4 (YPrime,I,Q,0.0);
     color.r = dot (yIQ,kYIQToR);
//  -->    color.g = dot (yIQ,kYIQToG); 
//  -->   color.b = dot (yIQ,kYIQToB);

     // Save the result
     gl_FragColor = color;
 }
);

但是,这张照片就是灰色/蓝色,被冲洗掉或是紫色的绿色.我在正确的轨道上吗？如果没有,如何修改此过滤器以影响个别渠道,同时保留其他渠道？

一些例子：

原来,我试图实现的效果：

(第二个图像几乎没有什么不同,然而红色通道的色调已经变得更加粉红色了,我需要能够在粉红色的橙色之间进行调整).

但是,这里是我得到的B和G评论：

(左侧：<0º,右侧：>0º) 它看起来像我不喜欢以红色的方式影响红色的色调;可能我正在接近这个错误,或者如果我在正确的轨道上,这段代码没有正确调整红色通道色调？ (我也尝试使用GPUImageColorMatrixFilter来实现这个效果,但是我并没有得到很多). 编辑：这是我现在使用@ VB_overflow的代码GPUImage包装器着色器的迭代,其功能上影响输入图像的方式类似于我的目标：

#import "GPUImageSkinToneFilter.h"

@implementation GPUImageSkinToneFilter

Nsstring *const kGPUImageSkinToneFragmentShaderString = SHADER_STRING
(
 varying highp vec2 textureCoordinate;

 uniform sampler2D inputimageTexture;

 // [-1;1] <=> [pink;orange]
 uniform highp float skinToneAdjust; // will make reds more pink

 // Other parameters
 uniform mediump float skinHue;
 uniform mediump float skinHueThreshold;
 uniform mediump float maxHueShift;
 uniform mediump float maxSaturationShift;

 // RGB <-> HSV conversion,thanks to http://lolengine.net/blog/2013/07/27/rgb-to-hsv-in-glsl
 highp vec3 rgb2hsv(highp vec3 c)
{
    highp vec4 K = vec4(0.0,-1.0 / 3.0,2.0 / 3.0,-1.0);
    highp vec4 p = mix(vec4(c.bg,K.wz),vec4(c.gb,K.xy),step(c.b,c.g));
    highp vec4 q = mix(vec4(p.xyw,c.r),vec4(c.r,p.yzx),step(p.x,c.r));

    highp float d = q.x - min(q.w,q.y);
    highp float e = 1.0e-10;
    return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)),d / (q.x + e),q.x);
}

 // HSV <-> RGB conversion,thanks to http://lolengine.net/blog/2013/07/27/rgb-to-hsv-in-glsl
 highp vec3 hsv2rgb(highp vec3 c)
{
    highp vec4 K = vec4(1.0,1.0 / 3.0,3.0);
    highp vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
    return c.z * mix(K.xxx,clamp(p - K.xxx,0.0,1.0),c.y);
}

 // Main
 void main ()
{

    // Sample the input pixel
    highp vec4 colorRGB = texture2D(inputimageTexture,textureCoordinate);

    // Convert color to HSV,extract hue
    highp vec3 colorHSV = rgb2hsv(colorRGB.rgb);
    highp float hue = colorHSV.x;

    // check how far from skin hue
    highp float dist = hue - skinHue;
    if (dist > 0.5)
        dist -= 1.0;
    if (dist < -0.5)
        dist += 1.0;
    dist = abs(dist)/0.5; // normalized to [0,1]

    // Apply Gaussian like filter
    highp float weight = exp(-dist*dist*skinHueThreshold);
    weight = clamp(weight,1.0);

    // We want more orange,so increase saturation
    if (skinToneAdjust > 0.0)
        colorHSV.y += skinToneAdjust * weight * maxSaturationShift;
    // we want more pinks,so decrease hue
    else
        colorHSV.x += skinToneAdjust * weight * maxHueShift;

    // final color
    highp vec3 finalColorRGB = hsv2rgb(colorHSV.rgb);

    // display
    gl_FragColor = vec4(finalColorRGB,1.0);
}
);

#pragma mark -
#pragma mark Initialization and teardown
@synthesize skinToneAdjust;
@synthesize skinHue;
@synthesize skinHueThreshold;
@synthesize maxHueShift;
@synthesize maxSaturationShift;

- (id)init
{
    if(! (self = [super initWithFragmentShaderFromString:kGPUImageSkinToneFragmentShaderString]) )
    {
        return nil;
    }

    skinToneAdjustUniform = [filterProgram uniformIndex:@"skinToneAdjust"];
    skinHueUniform = [filterProgram uniformIndex:@"skinHue"];
    skinHueThresholdUniform = [filterProgram uniformIndex:@"skinHueThreshold"];
    maxHueShiftUniform = [filterProgram uniformIndex:@"maxHueShift"];
    maxSaturationShiftUniform = [filterProgram uniformIndex:@"maxSaturationShift"];

    self.skinHue = 0.05;
    self.skinHueThreshold = 50.0;
    self.maxHueShift = 0.14;
    self.maxSaturationShift = 0.25;

    return self;
}

#pragma mark -
#pragma mark Accessors

- (void)setSkinToneAdjust:(CGFloat)newValue
{
    skinToneAdjust = newValue;
    [self setFloat:newValue forUniform:skinToneAdjustUniform program:filterProgram];
}

- (void)setSkinHue:(CGFloat)newValue
{
    skinHue = newValue;
    [self setFloat:newValue forUniform:skinHueUniform program:filterProgram];
}

- (void)setSkinHueThreshold:(CGFloat)newValue
{
    skinHueThreshold = newValue;
    [self setFloat:newValue forUniform:skinHueThresholdUniform program:filterProgram];
}

- (void)setMaxHueShift:(CGFloat)newValue
{
    maxHueShift = newValue;
    [self setFloat:newValue forUniform:maxHueShiftUniform program:filterProgram];
}

- (void)setMaxSaturationShift:(CGFloat)newValue
{
    maxSaturationShift = newValue;
    [self setFloat:newValue forUniform:maxSaturationShiftUniform program:filterProgram];
}

@end