HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 121

Chapter 4 D glDrawPixels glDrawPixels glDrawPixels: write a block of pixels to the frame buffer. C Specification void glDrawPixels( GLsizei width, GLsizei height, GLenum format, GLenum type, const GLvoid *pixels) Parameters width, height format type pixels Specify the dimensions of the pixel rectangle to be written into the frame buffer. Specifies the format of the pixel data. Symbolic constants GL_COLOR_INDEX, GL_STENCIL_INDEX, GL_DEPTH_COMPONENT, GL_RGBA, GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_LUMINANCE, and GL_LUMINANCE_ALPHA are accepted. Specifies the data type for pixels. Symbolic constants GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, and GL_FLOAT are accepted. Specifies a pointer to the pixel data. Description glDrawPixels reads pixel data from memory and writes it into the frame buffer relative to the current raster position. Use glRasterPos to set the current raster position; use glGet with argument GL_CURRENT_RASTER_POSITION to query the raster position. Several parameters define the encoding of pixel data in memory and control the processing of the pixel data before it is placed in the frame buffer. These parameters are set with four commands: glPixelStore, glPixelTransfer, glPixelMap, and glPixelZoom. This reference page describes the effects on glDrawPixels of many, but not all, of the parameters specified by these four commands. Data is read from pixels as a sequence of signed or unsigned bytes, signed or unsigned shorts, signed or unsigned integers, or single-precision floating-point values, depending on type. Each of these bytes, shorts, integers, or floating-point values is interpreted as one color or depth component, or one index, depending on format. Indices are always treated individually. Color components are treated as groups of one, two, three, or four values, again based on format. Both individual indices and groups of components are referred to as pixels. If type is GL_BITMAP, the data must be unsigned bytes, and format must be either GL_COLOR_INDEX or GL_STENCIL_INDEX. Each unsigned byte is treated as eight 1-bit pixels, with bit ordering determined by GL_UNPACK_LSB_FIRST (see glPixelStore). 121