Merge pull request BradLarson#1024 from jjxtra/master

Solid color generator filter alpha option

Author: BradLarson

framework/Source/GPUImageSolidColorGenerator.h

@@ -7,10 +7,12 @@
 @interface GPUImageSolidColorGenerator : GPUImageFilter
 {
     GLint colorUniform;
+    GLint useExistingAlphaUniform;
 }
 
 // This color dictates what the output image will be filled with
 @property(readwrite, nonatomic) GPUVector4 color;
+@property(readwrite, nonatomic, assign) BOOL useExistingAlpha; // whether to use the alpha of the existing image or not, default is NO
 
 - (void)setColorRed:(GLfloat)redComponent green:(GLfloat)greenComponent blue:(GLfloat)blueComponent alpha:(GLfloat)alphaComponent;
 

framework/Source/GPUImageSolidColorGenerator.m

@@ -4,30 +4,32 @@
 NSString *const kGPUSolidColorFragmentShaderString = SHADER_STRING
 (
  precision lowp float;
- 
+
  varying highp vec2 textureCoordinate;
- 
  uniform sampler2D inputImageTexture;
  uniform vec4 color;
- 
+ uniform float useExistingAlpha;
+
  void main()
  {
-     gl_FragColor = color;
+     lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
+     gl_FragColor = vec4(color.rgb, max(textureColor.a, 1.0 - useExistingAlpha));
  }
-);
+ );
 #else
 NSString *const kGPUSolidColorFragmentShaderString = SHADER_STRING
 (
  varying vec2 textureCoordinate;
- 
  uniform sampler2D inputImageTexture;
  uniform vec4 color;
- 
+ uniform float useExistingAlpha;
+
  void main()
  {
-     gl_FragColor = color;
+     vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
+     gl_FragColor = vec4(color.rgb, max(textureColor.a, 1.0 - useExistingAlpha));
  }
-);
+ );
 #endif
 
 @implementation GPUImageSolidColorGenerator
@@ -42,8 +44,10 @@ - (id)init;
     }
 
     colorUniform = [filterProgram uniformIndex:@"color"];
+    useExistingAlphaUniform = [filterProgram uniformIndex:@"useExistingAlpha"];
 
 	self.color = (GPUVector4){0.0f, 0.0f, 0.5f, 1.0f};
+    self.useExistingAlpha = NO;
 
     return self;
 }
@@ -65,7 +69,7 @@ - (void)forceProcessingAtSize:(CGSize)frameSize;
 - (void)addTarget:(id<GPUImageInput>)newTarget atTextureLocation:(NSInteger)textureLocation;
 {
     [super addTarget:newTarget atTextureLocation:textureLocation];
-    
+
     if (!CGSizeEqualToSize(inputTextureSize, CGSizeZero))
     {
         [newTarget setInputSize:inputTextureSize atIndex:textureLocation];
@@ -86,11 +90,13 @@ - (void)setColorRed:(GLfloat)redComponent green:(GLfloat)greenComponent blue:(GL
     _color.four = alphaComponent;
 
     [self setVec4:_color forUniform:colorUniform program:filterProgram];
-    
-    if (!CGSizeEqualToSize(inputTextureSize, CGSizeZero))
-    {
-        [self newFrameReadyAtTime:kCMTimeIndefinite atIndex:0];
-    }
+}
+
+- (void)setUseExistingAlpha:(BOOL)useExistingAlpha;
+{
+    _useExistingAlpha = useExistingAlpha;
+
+    [self setInteger:(useExistingAlpha ? 1 : 0) forUniform:useExistingAlphaUniform program:filterProgram];
 }
 
 @end