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glhistogram(3g) [osx man page]

GLHISTOGRAM(3G) 														   GLHISTOGRAM(3G)

NAME
glHistogram - define histogram table C SPECIFICATION
void glHistogram( GLenum target, GLsizei width, GLenum internalformat, GLboolean sink ) PARAMETERS
target The histogram whose parameters are to be set. Must be one of GL_HISTOGRAM or GL_PROXY_HISTOGRAM. width The number of entries in the histogram table. Must be a power of 2. internalformat The of entries in the histogram table. Must be one of GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_R3_G3_B2, GL_RGB, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12, GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12, or GL_RGBA16. sink If GL_TRUE, pixels will be consumed by the histogramming process and no drawing or texture loading will take place. If GL_FALSE, pixels will proceed to the minmax process after histogramming. DESCRIPTION
When GL_HISTOGRAM is enabled, RGBA color components are converted to histogram table indices by clamping to the range [0,1], multiplying by the width of the histogram table, and rounding to the nearest integer. The table entries selected by the RGBA indices are then incre- mented. (If the internal of the histogram table includes luminance, then the index derived from the R color component determines the luminance table entry to be incremented.) If a histogram table entry is incremented beyond its maximum value, then its value becomes unde- fined. (This is not an error.) Histogramming is performed only for RGBA pixels (though these may be specified originally as color indices and converted to RGBA by index table lookup). Histogramming is enabled with glEnable and disabled with glDisable. When target is GL_HISTOGRAM, glHistogram redefines the current histogram table to have width entries of the specified by internalformat. The entries are indexed 0 through width - 1, and all entries are initialized to zero. The values in the previous histogram table, if any, are lost. If sink is GL_TRUE, then pixels are discarded after histogramming; no further processing of the pixels takes place, and no draw- ing, texture loading, or pixel readback will result. When target is GL_PROXY_HISTOGRAM, glHistogram computes all state information as if the histogram table were to be redefined, but does not actually define the new table. If the requested histogram table is too large to be supported, then the state information will be set to zero. This provides a way to determine if a histogram table with the given parameters can be supported. NOTES
glHistogram is present only if GL_ARB_imaging is returned when glGetString is called with an argument of GL_EXTENSIONS. ERRORS
GL_INVALID_ENUM is generated if target is not one of the allowable values. GL_INVALID_VALUE is generated if width is less than zero or is not a power of 2. GL_INVALID_ENUM is generated if internalformat is not one of the allowable values. GL_TABLE_TOO_LARGE is generated if target is GL_HISTOGRAM and the histogram table specified is too large for the implementation. GL_INVALID_OPERATION is generated if glHistogram is executed between the execution of glBegin and the corresponding execution of glEnd. ASSOCIATED GETS
glGetHistogramParameter SEE ALSO
glGetHistogram, glResetHistogram GLHISTOGRAM(3G)

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GLMINMAX(3G)															      GLMINMAX(3G)

NAME
glMinmax - define minmax table C SPECIFICATION
void glMinmax( GLenum target, GLenum internalformat, GLboolean sink ) PARAMETERS
target The minmax table whose parameters are to be set. Must be GL_MINMAX. internalformat The of entries in the minmax table. Must be one of GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_R3_G3_B2, GL_RGB, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12, GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12, or GL_RGBA16. sink If GL_TRUE, pixels will be consumed by the minmax process and no drawing or texture loading will take place. If GL_FALSE, pixels will proceed to the final conversion process after minmax. DESCRIPTION
When GL_MINMAX is enabled, the RGBA components of incoming pixels are compared to the minimum and maximum values for each component, which are stored in the 2-element minmax table. (The first element stores the minima, and the second element stores the maxima.) If a pixel component is greater than the corresponding component in the maximum element, then the maximum element is updated with the pixel component value. If a pixel component is less than the corresponding component in the minimum element, then the minimum element is updated with the pixel component value. (In both cases, if the internal of the minmax table includes luminance, then the R color component of incoming pixels is used for comparison.) The contents of the minmax table may be retrieved at a later time by calling glGetMinmax. The minmax operation is enabled or disabled by calling glEnable or glDisable, respectively, with an argument of GL_MINMAX. glMinmax redefines the current minmax table to have entries of the specified by internalformat. The maximum element is initialized with the smallest possible component values, and the minimum element is initialized with the largest possible component values. The values in the previous minmax table, if any, are lost. If sink is GL_TRUE, then pixels are discarded after minmax; no further processing of the pix- els takes place, and no drawing, texture loading, or pixel readback will result. NOTES
glMinmax is present only if GL_ARB_imaging is returned when glGetString is called with an argument of GL_EXTENSIONS. ERRORS
GL_INVALID_ENUM is generated if target is not one of the allowable values. GL_INVALID_ENUM is generated if internalformat is not one of the allowable values. GL_INVALID_OPERATION is generated if glMinmax is executed between the execution of glBegin and the corresponding execution of glEnd. ASSOCIATED GETS
glGetMinmaxParameter SEE ALSO
glGetMinmax, glResetMinmax GLMINMAX(3G)
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