Use default number of channels in STB image loading

This fixes instances where different number of channels are available
than those requested.

Author: queueRAM

n64graphics.c

@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <strings.h>
 
 #define STBI_NO_LINEAR
 #define STBI_NO_HDR
@@ -376,7 +377,7 @@ rgba *png2rgba(const char *png_filename, int *width, int *height)
    int channels = 0;
    int img_size;
 
-   stbi_uc *data = stbi_load(png_filename, &w, &h, &channels, 4);
+   stbi_uc *data = stbi_load(png_filename, &w, &h, &channels, STBI_default);
    if (!data || w <= 0 || h <= 0) {
       ERROR("Error loading \"%s\"\n", png_filename);
       return NULL;
@@ -432,15 +433,14 @@ rgba *png2rgba(const char *png_filename, int *width, int *height)
    return img;
 }
 
-// save IA data to grayscale PNG file
 ia *png2ia(const char *png_filename, int *width, int *height)
 {
    ia *img = NULL;
    int w = 0, h = 0;
    int channels = 0;
    int img_size;
 
-   stbi_uc *data = stbi_load(png_filename, &w, &h, &channels, 2);
+   stbi_uc *data = stbi_load(png_filename, &w, &h, &channels, STBI_default);
    if (!data || w <= 0 || h <= 0) {
       ERROR("Error loading \"%s\"\n", png_filename);
       return NULL;