WebGLRenderingContext.blendFunc()

The WebGLRenderingContext.blendFunc() method of the WebGL API defines which function is used for blending pixel arithmetic.

Syntax

void gl.blendFunc(sfactor, dfactor);

Parameters

sfactor
A GLenum specifying a multiplier for the source blending factors. The default value is gl.ONE. For possible values, see below.
dfactor
A GLenum specifying a multiplier for the destination blending factors. The default value is gl.ZERO. For possible values, see below.

Return value

None.

Exceptions

  • If sfactor or dfactor is not one of the listed possible values, a gl.INVALID_ENUM error is thrown.
  • If a constant color and a constant alpha value are used together as source and destination factors, a gl.INVALID_ENUM error is thrown.

Constants

The following constants can be used for sfactor and dfactor.

The formula for the blending color can be described like this: color(RGBA) = (sourceColor * sfactor) + (destinationColor * dfactor). The RBGA values are between 0 and 1.

Constant Factor Description
gl.ZERO 0,0,0,0 Multiplies all colors by 0.
gl.ONE 1,1,1,1 Multiplies all colors by 1.
gl.SRC_COLOR RS, GS, BS, AS Multiplies all colors by the source colors.
gl.ONE_MINUS_SRC_COLOR 1-RS, 1-GS, 1-BS, 1-AS Multiplies all colors by 1 minus each source color.
gl.DST_COLOR RD, GD, BD, AD Multiplies all colors by the destination color.
gl.ONE_MINUS_DST_COLOR 1-RD, 1-GD, 1-BD, 1-AD Multiplies all colors by 1 minus each destination color.
gl.SRC_ALPHA AS, AS, AS, AS Multiplies all colors by the source alpha value.
gl.ONE_MINUS_SRC_ALPHA 1-AS, 1-AS, 1-AS, 1-AS Multiplies all colors by 1 minus the source alpha value.
gl.DST_ALPHA AD, AD, AD, AD Multiplies all colors by the destination alpha value.
gl.ONE_MINUS_DST_ALPHA 1-AD, 1-AD, 1-AD, 1-AD Multiplies all colors by 1 minus the destination alpha value.
gl.CONSTANT_COLOR RC, GC, BC, AC Multiplies all colors by a constant color.
gl.ONE_MINUS_CONSTANT_COLOR 1-RC, 1-GC, 1-BC, 1-AC Multiplies all colors by 1 minus a constant color.
gl.CONSTANT_ALPHA AC, AC, AC, AC Multiplies all colors by a constant alpha value.
gl.ONE_MINUS_CONSTANT_ALPHA 1-AC, 1-AC, 1-AC, 1-AC Multiplies all colors by 1 minus a constant alpha value.
gl.SRC_ALPHA_SATURATE

min(AS, 1 - AD), min(AS, 1 - AD), min(AS, 1 - AD), 1

 Multiplies the RGB colors by the smaller of either the source alpha value or the value of 1 minus the destination alpha value. The alpha value is multiplied by 1.

Examples

To use the blend function, you first have to activate blending with WebGLRenderingContext.enable() with the argument gl.BLEND.

gl.enable(gl.BLEND);
gl.blendFunc(gl.SRC_COLOR, gl.DST_COLOR);

To get the current blend function, query the BLEND_SRC_RGB, BLEND_SRC_ALPHA, BLEND_DST_RGB, and BLEND_DST_ALPHA constants which return one of the blend function constants.

gl.enable(gl.BLEND);
gl.blendFunc(gl.SRC_COLOR, gl.DST_COLOR);
gl.getParameter(gl.BLEND_SRC_RGB) == gl.SRC_COLOR;
// true

Specifications

Specification Status Comment
WebGL 1.0
The definition of 'blendFunc' in that specification.		 Recommendation Initial definition.
In WebGL, constant color and constant alpha cannot be used together as source and destination factors in the blend function. See section 6.13. of the specification.
OpenGL ES 2.0
The definition of 'glBlendFunc' in that specification.		 Standard Man page of the OpenGL API.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
blendFuncChrome Full support 9Edge Full support 12Firefox Full support 4IE Full support 11Opera Full support 12Safari Full support 5.1WebView Android Full support YesChrome Android Full support 25Firefox Android Full support YesOpera Android Full support 12Safari iOS Full support 8Samsung Internet Android Full support 1.5

Legend

Full support  
Full support

See also

Related Topics
  1. WebGL API
  2. WebGLRenderingContext
  3. Properties
    1. canvas
    2. drawingBufferHeight
    3. drawingBufferWidth
  4. Methods
    1. activeTexture()
    2. attachShader()
    3. bindAttribLocation()
    4. bindBuffer()
    5. bindFramebuffer()
    6. bindRenderbuffer()
    7. bindTexture()
    8. blendColor()
    9. blendEquation()
    10. blendEquationSeparate()
    11. blendFunc()
    12. blendFuncSeparate()
    13. bufferData()
    14. bufferSubData()
    15. checkFramebufferStatus()
    16. clear()
    17. clearColor()
    18. clearDepth()
    19. clearStencil()
    20. colorMask()
    21. commit()
    22. compileShader()
    23. compressedTexImage[23]D()
    24. compressedTexSubImage2D()
    25. copyTexImage2D()
    26. copyTexSubImage2D()
    27. createBuffer()
    28. createFramebuffer()
    29. createProgram()
    30. createRenderbuffer()
    31. createShader()
    32. createTexture()
    33. cullFace()
    34. deleteBuffer()
    35. deleteFramebuffer()
    36. deleteProgram()
    37. deleteRenderbuffer()
    38. deleteShader()
    39. deleteTexture()
    40. depthFunc()
    41. depthMask()
    42. depthRange()
    43. detachShader()
    44. disable()
    45. disableVertexAttribArray()
    46. drawArrays()
    47. drawElements()
    48. enable()
    49. enableVertexAttribArray()
    50. finish()
    51. flush()
    52. framebufferRenderbuffer()
    53. framebufferTexture2D()
    54. frontFace()
    55. generateMipmap()
    56. getActiveAttrib()
    57. getActiveUniform()
    58. getAttachedShaders()
    59. getAttribLocation()
    60. getBufferParameter()
    61. getContextAttributes()
    62. getError()
    63. getExtension()
    64. getFramebufferAttachmentParameter()
    65. getParameter()
    66. getProgramInfoLog()
    67. getProgramParameter()
    68. getRenderbufferParameter()
    69. getShaderInfoLog()
    70. getShaderParameter()
    71. getShaderPrecisionFormat()
    72. getShaderSource()
    73. getSupportedExtensions()
    74. getTexParameter()
    75. getUniform()
    76. getUniformLocation()
    77. getVertexAttrib()
    78. getVertexAttribOffset()
    79. hint()
    80. isBuffer()
    81. isContextLost()
    82. isEnabled()
    83. isFramebuffer()
    84. isProgram()
    85. isRenderbuffer()
    86. isShader()
    87. isTexture()
    88. lineWidth()
    89. linkProgram()
    90. pixelStorei()
    91. polygonOffset()
    92. readPixels()
    93. renderbufferStorage()
    94. sampleCoverage()
    95. scissor()
    96. shaderSource()
    97. stencilFunc()
    98. stencilFuncSeparate()
    99. stencilMask()
    100. stencilMaskSeparate()
    101. stencilOp()
    102. stencilOpSeparate()
    103. texImage2D()
    104. texParameter[fi]()
    105. texSubImage2D()
    106. uniform[1234][fi][v]()
    107. uniformMatrix[234]fv()
    108. useProgram()
    109. validateProgram()
    110. vertexAttrib[1234]f[v]()
    111. vertexAttribPointer()
    112. viewport()
  5. Related pages for WebGL
    1. ANGLE_instanced_arrays
    2. EXT_blend_minmax
    3. EXT_color_buffer_half_float
    4. EXT_disjoint_timer_query
    5. EXT_frag_depth
    6. EXT_sRGB
    7. EXT_shader_texture_lod
    8. EXT_texture_filter_anisotropic
    9. OES_element_index_uint
    10. OES_standard_derivatives
    11. OES_texture_float
    12. OES_texture_float_linear
    13. OES_texture_half_float
    14. OES_texture_half_float_linear
    15. OES_vertex_array_object
    16. WEBGL_color_buffer_float
    17. WEBGL_compressed_texture_atc
    18. WEBGL_compressed_texture_etc1
    19. WEBGL_compressed_texture_pvrtc
    20. WEBGL_compressed_texture_s3tc
    21. WEBGL_compressed_texture_s3tc_srgb
    22. WEBGL_debug_renderer_info
    23. WEBGL_debug_shaders
    24. WEBGL_depth_texture
    25. WEBGL_draw_buffers
    26. WEBGL_lose_context
    27. WebGL2RenderingContext
    28. WebGLActiveInfo
    29. WebGLBuffer
    30. WebGLContextEvent
    31. WebGLFramebuffer
    32. WebGLObject
    33. WebGLProgram
    34. WebGLQuery
    35. WebGLRenderbuffer
    36. WebGLSampler
    37. WebGLShader
    38. WebGLShaderPrecisionFormat
    39. WebGLSync
    40. WebGLTexture
    41. WebGLTransformFeedback
    42. WebGLUniformLocation
    43. WebGLVertexArrayObject