glDrawPixels

glDrawPixels: man2/glDrawPixels.xml

glDrawPixels reads pixel data from memory and writes it into the frame buffer relative to the current raster position, provided that the raster position is valid. Use glRasterPos or glWindowPos to set the current raster position; use glGet with argument GL_CURRENT_RASTER_POSITION_VALID to determine if the specified raster position is valid, and 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 data 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. When type is one of GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, or GL_FLOAT each of these bytes, shorts, integers, or floating-point values is interpreted as one color or depth component, or one index, depending on format. When type is one of GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_INT_8_8_8_8, or GL_UNSIGNED_INT_10_10_10_2, each unsigned value is interpreted as containing all the components for a single pixel, with the color components arranged according to format. When type is one of GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8_REV, or GL_UNSIGNED_INT_2_10_10_10_REV, each unsigned value is interpreted as containing all color components, specified by format, for a single pixel in a reversed order. 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 ). width × height pixels are read from memory, starting at location data. By default, these pixels are taken from adjacent memory locations, except that after all width pixels are read, the read pointer is advanced to the next four-byte boundary. The four-byte row alignment is specified by glPixelStore with argument GL_UNPACK_ALIGNMENT, and it can be set to one, two, four, or eight bytes. Other pixel store parameters specify different read pointer advancements, both before the first pixel is read and after all width pixels are read. See the glPixelStore reference page for details on these options. If a non-zero named buffer object is bound to the GL_PIXEL_UNPACK_BUFFER target (see glBindBuffer ) while a block of pixels is specified, data is treated as a byte offset into the buffer object's data store. The width × height pixels that are read from memory are each operated on in the same way, based on the values of several parameters specified by glPixelTransfer and glPixelMap. The details of these operations, as well as the target buffer into which the pixels are drawn, are specific to the format of the pixels, as specified by format. format can assume one of 13 symbolic values: The following table summarizes the meaning of the valid constants for the parameter: Type Corresponding Type GL_UNSIGNED_BYTE unsigned 8-bit integer GL_BYTE signed 8-bit integer GL_BITMAP single bits in unsigned 8-bit integers GL_UNSIGNED_SHORT unsigned 16-bit integer GL_SHORT signed 16-bit integer GL_UNSIGNED_INT unsigned 32-bit integer GL_INT 32-bit integer GL_FLOAT single-precision floating-point GL_UNSIGNED_BYTE_3_3_2 unsigned 8-bit integer GL_UNSIGNED_BYTE_2_3_3_REV unsigned 8-bit integer with reversed component ordering GL_UNSIGNED_SHORT_5_6_5 unsigned 16-bit integer GL_UNSIGNED_SHORT_5_6_5_REV unsigned 16-bit integer with reversed component ordering GL_UNSIGNED_SHORT_4_4_4_4 unsigned 16-bit integer GL_UNSIGNED_SHORT_4_4_4_4_REV unsigned 16-bit integer with reversed component ordering GL_UNSIGNED_SHORT_5_5_5_1 unsigned 16-bit integer GL_UNSIGNED_SHORT_1_5_5_5_REV unsigned 16-bit integer with reversed component ordering GL_UNSIGNED_INT_8_8_8_8 unsigned 32-bit integer GL_UNSIGNED_INT_8_8_8_8_REV unsigned 32-bit integer with reversed component ordering GL_UNSIGNED_INT_10_10_10_2 unsigned 32-bit integer GL_UNSIGNED_INT_2_10_10_10_REV unsigned 32-bit integer with reversed component ordering The rasterization described so far assumes pixel zoom factors of 1. If glPixelZoom is used to change the x and y pixel zoom factors, pixels are converted to fragments as follows. If x r y r is the current raster position, and a given pixel is in the n th column and m th row of the pixel rectangle, then fragments are generated for pixels whose centers are in the rectangle with corners at x r + zoom x ⁢ n y r + zoom y ⁢ m x r + zoom x ⁡ n + 1 y r + zoom y ⁡ m + 1 where zoom x is the value of GL_ZOOM_X and zoom y is the value of GL_ZOOM_Y.

GL_BGR and GL_BGRA are only valid for format if the GL version is 1.2 or greater. GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, and GL_UNSIGNED_INT_2_10_10_10_REV are only valid for type if the GL version is 1.2 or greater.