Thank you for your reply, your answers cleared up a lot of my confusion.
I have resolved my problems getting programs to compile to your comment that IMG_LoadTexture is part of SDL_image.h. I am using a fresh install of SDL2 and there isn’t an 'SDL2/SDL_image.h’ file.
Because of this I am also receiving errors for SDL_SetVideoMode, SDL_UpdateRect.
I have installed SDL_image.h and receive this message.
Error messages
main.c: In function ‘int SDL_main()’:
main.c:38:14: error: ‘SDL_SetVideoMode’ was not declared in this scope
screen = SDL_SetVideoMode(256, 256, 16, 0);
^~~~~~~~~~~~~~~~
main.c:38:14: note: suggested alternative: ‘SDL_GetVideoDriver’
screen = SDL_SetVideoMode(256, 256, 16, 0);
^~~~~~~~~~~~~~~~
SDL_GetVideoDriver
main.c:71:5: error: ‘SDL_UpdateRect’ was not declared in this scope
SDL_UpdateRect(screen, 0, 0, 0, 0);
^~~~~~~~~~~~~~
main.c:71:5: note: suggested alternative: ‘SDL_UpdateTexture’
SDL_UpdateRect(screen, 0, 0, 0, 0);
^~~~~~~~~~~~~~
SDL_UpdateTexture
Press any key to continue . . .
Full code
/* Example of direct pixel access with SDL. */
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <SDL2/SDL_rect.h>
#include <stdio.h>
#include <stdlib.h>
Uint16 CreateHicolorPixel(SDL_PixelFormat * fmt, Uint8 red,
Uint8 green, Uint8 blue)
{
Uint16 value;
/* This series of bit shifts uses the information from the
SDL_Format structure to correctly compose a 16-bit pixel
value from 8-bit red, green, and blue data. */
value = ((red >> fmt->Rloss) << fmt->Rshift) +
((green >> fmt->Gloss) << fmt->Gshift) +
((blue >> fmt->Bloss) << fmt->Bshift);
return value;
}
int main()
{
SDL_Surface *screen;
Uint16 *raw_pixels;
int x, y;
/* Initialize SDL's video system and check for errors. */
if (SDL_Init(SDL_INIT_VIDEO) != 0) {
printf("Unable to initialize SDL: %s\n", SDL_GetError());
return 1;
}
/* Make sure SDL_Quit gets called when the program exits! */
atexit(SDL_Quit);
/* Attempt to set a 256x256 hicolor (16-bit) video mode.
This will set some type of 16-bit mode, but we won't
know which particular pixel format ahead of time. If
the video card can't handle hicolor modes, SDL will
emulate it. */
screen = SDL_SetVideoMode(256, 256, 16, 0);
if (screen == NULL) {
printf("Unable to set video mode: %s\n", SDL_GetError());
return 1;
}
/* Video memory can be strange, and it's sometimes necessary to
"lock" it before it can be modified. SDL abstracts this with
the SDL_LockSurface function. */
SDL_LockSurface(screen);
/* Get a pointer to the video surface's memory. */
raw_pixels = (Uint16 *) screen->pixels;
/* We can now safely write to the video surface. We'll draw a
nice gradient pattern by varying our red and blue components
along the X and Y axes. Notice the formula used to calculate
the offset into the framebuffer for each pixel.
(The pitch is the number of bytes per scanline in memory.) */
for (x = 0; x < 256; x++) {
for (y = 0; y < 256; y++) {
Uint16 pixel_color;
int offset;
pixel_color = CreateHicolorPixel(screen->format,
x, 0, y);
offset = (screen->pitch / 2 * y + x);
raw_pixels[offset] = pixel_color;
}
}
/* We're finished drawing, so unlock the surface. */
SDL_UnlockSurface(screen);
/* Inform SDL that the screen has been changed. This is
necessary because SDL's screen surface is not always the real
framebuffer; it is sometimes emulated behind the scenes. */
SDL_UpdateRect(screen, 0, 0, 0, 0);
/* Pause for a few seconds as the viewer gasps in awe. */
SDL_Delay(3000);
return 0;
}