This function must be called for any image constructed by the client before passing it to any other Xlib function. Image structures created or returned by Xlib do not need to be initialized in this fashion.
This function returns a nonzero status if initialization of the structure is successful. It returns zero if it detected some error or inconsistency in the structure, in which case the image is not changed.
The _X_C_r_e_a_t_e_I_m_a_g_e function allocates the memory needed for an _X_I_m_a_g_e structure for the specified display but does not allocate space for the image itself. Rather, it initializes the structure byte-order, bit-order, and bitmap-unit values from the display and returns a pointer to the _X_I_m_a_g_e structure. The red, green, and blue mask values are defined for Z format images only and are derived from the _V_i_s_u_a_l structure passed in. Other values also are passed in. The offset permits the rapid displaying of the image without requiring each scanline to be shifted into position. If you pass a zero value in bytes_per_line, Xlib assumes that the scanlines are contiguous in memory and calculates the value of bytes_per_line itself.
Note that when the image is created using _X_C_r_e_a_t_e_I_m_a_g_e, _X_G_e_t_I_m_a_g_e, or _X_S_u_b_I_m_a_g_e, the destroy procedure that the _X_D_e_s_t_r_o_y_I_m_a_g_e function calls frees both the image structure and the data pointed to by the image structure.
The basic functions used to get a pixel, set a pixel, create a subimage, and add a constant value to an image are defined in the image object. The functions in this section are really macro invocations of the functions in the image object and are defined in <_X_1_1_/_X_u_t_i_l_._h>.
The _X_G_e_t_P_i_x_e_l function returns the specified pixel from the named image. The pixel value is returned in normalized format (that is, the least significant byte of the long is the least significant byte of the pixel). The image must contain the x and y coordinates.
The _X_P_u_t_P_i_x_e_l function overwrites the pixel in the named image with the specified pixel value. The input pixel value must be in normalized format (that is, the least significant byte of the long is the least significant byte of the pixel). The image must contain the x and y coordinates.
The _X_S_u_b_I_m_a_g_e function creates a new image that is a subsection of an existing one. It allocates the memory necessary for the new _X_I_m_a_g_e structure and returns a pointer to the new image. The data is copied from the source image, and the image must contain the rectangle defined by x, y, subimage_width, and subimage_height.
The _X_A_d_d_P_i_x_e_l function adds a constant value to every pixel in an image. It is useful when you have a base pixel value from allocating color resources and need to manipulate the image to that form.
The _X_D_e_s_t_r_o_y_I_m_a_g_e function deallocates the memory associated with the _X_I_m_a_g_e structure.