Glreadpixels - HP b2600 Reference Manual
Opengl 1.1 reference
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glReadPixels
glReadPixels
glReadPixels: read a block of pixels from the frame buffer.
C Specification
void glReadPixels(
Parameters
x, y
width, height
format
type
pixels
Description
glReadPixels returns pixel data from the frame buffer, starting with the pixel whose
lower left corner is at location (x, y), into client memory starting at location pixels.
Several parameters control the processing of the pixel data before it is placed into client
memory. These parameters are set with three commands: glPixelStore, glPixelTransfer,
and glPixelMap. This reference page describes the effects on glReadPixels of most, but
not all of the parameters specified by these three commands.
glReadPixels returns values from each pixel with lower left corner at (x + i, y + j) for 0
< width and 0
returned in row order from the lowest to the highest row, left to right in each row.
format specifies the format for the returned pixel values; accepted values are:
GL_COLOR_INDEX
380
GLint x,
GLint y,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
GLvoid *pixels)
Specify the window coordinates of the first pixel that is read from the
frame buffer. This location is the lower left corner of a rectangular
block of pixels.
Specify the dimensions of the pixel rectangle. width and height of one
correspond to a single pixel.
Specifies the format of the pixel data. The following symbolic values
are accepted: GL_COLOR_INDEX, GL_STENCIL_INDEX,
GL_DEPTH_COMPONENT, GL_RED, GL_GREEN, GL_BLUE,
GL_ALPHA, GL_RGB, GL_RGBA, GL_LUMINANCE, and
GL_LUMINANCE_ALPHA.
Specifies the data type of the pixel data. Must be one of
GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP,
GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT,
GL_INT, or GL_FLOAT.
Returns the pixel data.
j < height. This pixel is said to be the ith pixel in the jth row. Pixels are
i
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