GPUImage定制的OpenGL ES着色器产生黑色图像

Question

基于this另一OpenGL ES的图像过滤器工作：

uniform sampler2D texture; 
uniform float amount; 
uniform vec2 texSize; 
varying vec2 texCoord; 
void main() { 
    vec4 color = texture2D(texture, texCoord); 
    vec4 orig = color; 

    /* High pass filter */ 
    vec4 highpass = color * 5.0; 

    float dx = 1.0/texSize.x; 
    float dy = 1.0/texSize.y; 
    highpass += texture2D(texture, texCoord + vec2(-dx, -dy)) * -0.625; 
    highpass += texture2D(texture, texCoord + vec2(dx, -dy)) * -0.625; 
    highpass += texture2D(texture, texCoord + vec2(dx, dy)) * -0.625; 
    highpass += texture2D(texture, texCoord + vec2(-dx, dy)) * -0.625; 
    highpass += texture2D(texture, texCoord + vec2(-dx * 2.0, -dy * 2.0)) * -0.625; 
    highpass += texture2D(texture, texCoord + vec2(dx * 2.0, -dy * 2.0)) * -0.625; 
    highpass += texture2D(texture, texCoord + vec2(dx * 2.0, dy * 2.0)) * -0.625; 
    highpass += texture2D(texture, texCoord + vec2(-dx * 2.0, dy * 2.0)) * -0.625; 
    highpass.a = 1.0; 

    /* Overlay blend */ 
    vec3 overlay = vec3(1.0); 
    if (highpass.r <= 0.5) { 
     overlay.r = 2.0 * color.r * highpass.r; 
    } else { 
     overlay.r = 1.0 - 2.0 * (1.0 - color.r) * (1.0 - highpass.r); 
    } 
    if (highpass.g <= 0.5) { 
     overlay.g = 2.0 * color.g * highpass.g; 
    } else { 
     overlay.g = 1.0 - 2.0 * (1.0 - color.g) * (1.0 - highpass.g); 
    } 
    if (highpass.b <= 0.5) { 
     overlay.b = 2.0 * color.b * highpass.b; 
    } else { 
     overlay.b = 1.0 - 2.0 * (1.0 - color.b) * (1.0 - highpass.b); 
    } 
    color.rgb = (overlay * 0.8) + (orig.rgb * 0.2); 

    /* Desaturated hard light */ 
    vec3 desaturated = vec3(orig.r + orig.g + orig.b/3.0); 
    if (desaturated.r <= 0.5) { 
     color.rgb = 2.0 * color.rgb * desaturated; 
    } else { 
     color.rgb = vec3(1.0) - vec3(2.0) * (vec3(1.0) - color.rgb) * (vec3(1.0) - desaturated); 
    } 
    color = (orig * 0.6) + (color * 0.4); 

    /* Add back some color */ 
    float average = (color.r + color.g + color.b)/3.0; 
    color.rgb += (average - color.rgb) * (1.0 - 1.0/(1.001 - 0.45)); 

    gl_FragColor = (color * amount) + (orig * (1.0 - amount)); 
} 

按我question yesterday，我知道分配精度每个浮点和VEC。这一次它编译得很好，但是当我在GPUImage中应用过滤器时（例如，通过将clarity的值设置为0.8），图像变黑。我的直觉告诉我这与纹理大小有关，但不知道GPUImage如何处理，我有点卡住了。

这是我在Objective-C实现：我想这样做的

.H

#import <GPUImage/GPUImage.h> 

@interface GPUImageClarityFilter : GPUImageFilter 
{ 
    GLint clarityUniform; 
} 

// Gives the image a gritty, surreal contrasty effect 
// Value 0 to 1 
@property (readwrite, nonatomic) GLfloat clarity; 

@end 

.M

#import "GPUImageClarityFilter.h" 

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE 
NSString *const kGPUImageClarityFragmentShaderString = SHADER_STRING 
(
uniform sampler2D inputImageTexture; 
uniform lowp float clarity; 
uniform highp vec2 textureSize; 
varying highp vec2 textureCoordinate; 
void main() { 
    highp vec4 color = texture2D(inputImageTexture, textureCoordinate); 
    highp vec4 orig = color; 

    /* High pass filter */ 
    highp vec4 highpass = color * 5.0; 

    highp float dx = 1.0/textureSize.x; 
    highp float dy = 1.0/textureSize.y; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx, -dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx, -dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx, dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx, dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx * 2.0, -dy * 2.0)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx * 2.0, -dy * 2.0)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx * 2.0, dy * 2.0)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx * 2.0, dy * 2.0)) * -0.625; 
    highpass.a = 1.0; 

    /* Overlay blend */ 
    highp vec3 overlay = vec3(1.0); 
    if (highpass.r <= 0.5) { 
     overlay.r = 2.0 * color.r * highpass.r; 
    } else { 
     overlay.r = 1.0 - 2.0 * (1.0 - color.r) * (1.0 - highpass.r); 
    } 
    if (highpass.g <= 0.5) { 
     overlay.g = 2.0 * color.g * highpass.g; 
    } else { 
     overlay.g = 1.0 - 2.0 * (1.0 - color.g) * (1.0 - highpass.g); 
    } 
    if (highpass.b <= 0.5) { 
     overlay.b = 2.0 * color.b * highpass.b; 
    } else { 
     overlay.b = 1.0 - 2.0 * (1.0 - color.b) * (1.0 - highpass.b); 
    } 
    color.rgb = (overlay * 0.8) + (orig.rgb * 0.2); 

    /* Desaturated hard light */ 
    highp vec3 desaturated = vec3(orig.r + orig.g + orig.b/3.0); 
    if (desaturated.r <= 0.5) { 
     color.rgb = 2.0 * color.rgb * desaturated; 
    } else { 
     color.rgb = vec3(1.0) - vec3(2.0) * (vec3(1.0) - color.rgb) * (vec3(1.0) - desaturated); 
    } 
    color = (orig * 0.6) + (color * 0.4); 

    /* Add back some color */ 
    highp float average = (color.r + color.g + color.b)/3.0; 
    color.rgb += (average - color.rgb) * (1.0 - 1.0/(1.001 - 0.45)); 

    gl_FragColor = (color * clarity) + (orig * (1.0 - clarity)); 
} 
); 
#else 
NSString *const kGPUImageClarityFragmentShaderString = SHADER_STRING 
(
uniform sampler2D inputImageTexture; 
uniform float clarity; 
uniform vec2 textureSize; 
varying vec2 textureCoordinate; 
void main() { 
    vec4 color = texture2D(inputImageTexture, textureCoordinate); 
    vec4 orig = color; 

    /* High pass filter */ 
    vec4 highpass = color * 5.0; 

    float dx = 1.0/textureSize.x; 
    float dy = 1.0/textureSize.y; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx, -dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx, -dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx, dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx, dy)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx * 2.0, -dy * 2.0)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx * 2.0, -dy * 2.0)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(dx * 2.0, dy * 2.0)) * -0.625; 
    highpass += texture2D(inputImageTexture, textureCoordinate + vec2(-dx * 2.0, dy * 2.0)) * -0.625; 
    highpass.a = 1.0; 

    /* Overlay blend */ 
    vec3 overlay = vec3(1.0); 
    if (highpass.r <= 0.5) { 
     overlay.r = 2.0 * color.r * highpass.r; 
    } else { 
     overlay.r = 1.0 - 2.0 * (1.0 - color.r) * (1.0 - highpass.r); 
    } 
    if (highpass.g <= 0.5) { 
     overlay.g = 2.0 * color.g * highpass.g; 
    } else { 
     overlay.g = 1.0 - 2.0 * (1.0 - color.g) * (1.0 - highpass.g); 
    } 
    if (highpass.b <= 0.5) { 
     overlay.b = 2.0 * color.b * highpass.b; 
    } else { 
     overlay.b = 1.0 - 2.0 * (1.0 - color.b) * (1.0 - highpass.b); 
    } 
    color.rgb = (overlay * 0.8) + (orig.rgb * 0.2); 

    /* Desaturated hard light */ 
    vec3 desaturated = vec3(orig.r + orig.g + orig.b/3.0); 
    if (desaturated.r <= 0.5) { 
     color.rgb = 2.0 * color.rgb * desaturated; 
    } else { 
     color.rgb = vec3(1.0) - vec3(2.0) * (vec3(1.0) - color.rgb) * (vec3(1.0) - desaturated); 
    } 
    color = (orig * 0.6) + (color * 0.4); 

    /* Add back some color */ 
    float average = (color.r + color.g + color.b)/3.0; 
    color.rgb += (average - color.rgb) * (1.0 - 1.0/(1.001 - 0.45)); 

    gl_FragColor = (color * clarity) + (orig * (1.0 - clarity)); 
} 
); 
#endif 

@implementation GPUImageClarityFilter 

@synthesize clarity = _clarity; 

#pragma mark - 
#pragma mark Initialization and teardown 

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

    clarityUniform = [filterProgram uniformIndex:@"clarity"]; 
    self.clarity = 0.0; 

    return self; 
} 

#pragma mark - 
#pragma mark Accessors 

- (void)setClarity:(GLfloat)clarity; 
{ 
    _clarity = clarity; 

    [self setFloat:_clarity forUniform:clarityUniform program:filterProgram]; 
} 

@end 

的另一件事是运用GPUImage的内置在低通和高通滤波器中，但我感觉这会导致相当笨重的s olution。

Answer 1

这可能是由于textureSize不是作为GPUImageFilter的一部分提供给您的标准制服。 inputImageTexture和textureCoordinate是由其中一个过滤器提供的标准制服，看起来您正在提供clarity制服。

因为没有设置textureSize，所以它将默认为0.0。然后您的1.0/textureSize.x计算将被零除，这往往会导致iOS片段着色器中的黑帧。

您可以计算并提供该制服，或者改为使用GPUImage3x3TextureSamplingFilter替代您的自定义过滤器。该过滤器基类将1.0/textureSize.x的结果作为texelWidth统一（以及对于垂直分量的匹配texelHeight）。你不必计算这个。实际上，它也会计算周围8个像素的纹理坐标，因此您可以切除上述四个计算并将其转换为非依赖性纹理读取。您只需计算基于2 * texelWidth和2 * texelHeight的四个纹理读取即可完成剩余的四次读取。

实际上，您可以将此操作分解为多个通道，以节省计算量，进行小方框模糊处理，然后进行叠加混合处理，然后执行此过滤器的最后一个阶段。这可以进一步加快这一进程。

Answer 2

所以，你可以重写

(void)setupFilterForSize:(CGSize)filterFrameSize 

方法设置宽度&高度因子样GPUImageSharpenFilter。