From b6b9b5084fc482df71b020897453e63f55ec2726 Mon Sep 17 00:00:00 2001
From: Harry Jeffery <harry@exec64.co.uk>
Date: Thu, 5 Nov 2015 20:53:11 +0000
Subject: Add a PNG loader

---
 Makefile |  2 +-
 loader.c | 10 +++++++---
 png.c    | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 4 deletions(-)
 create mode 100644 png.c

diff --git a/Makefile b/Makefile
index 87b2fb1..7c23259 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 .PHONY: clean
 
 CFLAGS = -g -W -Wall -std=c11 `sdl2-config --cflags`
-LDFLAGS = `sdl2-config --libs`
+LDFLAGS = `sdl2-config --libs` -lpng
 
 TARGET = imv
 SOURCES = $(wildcard *.c)
diff --git a/loader.c b/loader.c
index 0a94cf9..9f62d24 100644
--- a/loader.c
+++ b/loader.c
@@ -1,13 +1,14 @@
 #include <SDL2/SDL.h>
 #include <string.h>
 
+extern SDL_Texture* imv_load_png(SDL_Renderer *r, const char* path);
+
 SDL_Texture* imv_load_image(SDL_Renderer *r, const char* path)
 {
   if(!path)
     return NULL;
 
   const char* ext = strrchr(path, '.');
-  SDL_Texture *img = NULL;
   if(ext == NULL) {
     fprintf(stderr,
         "Could not determine filetype of '%s' from its extension.\n",
@@ -15,7 +16,7 @@ SDL_Texture* imv_load_image(SDL_Renderer *r, const char* path)
   } else if(strcasecmp(ext, ".test") == 0) {
     const int width = 1280;
     const int height = 720;
-    img = SDL_CreateTexture(r,
+    SDL_Texture *img = SDL_CreateTexture(r,
         SDL_PIXELFORMAT_RGB888, SDL_TEXTUREACCESS_STATIC,
         width, height);
     void *pixels = malloc(width*height*3);
@@ -23,7 +24,10 @@ SDL_Texture* imv_load_image(SDL_Renderer *r, const char* path)
     SDL_Rect area = {0,0,width,height};
     SDL_UpdateTexture(img, &area, pixels, width * 3);
     free(pixels);
+    return img;
+  } else if(strcasecmp(ext, ".png") == 0) {
+    return imv_load_png(r, path);
   }
 
-  return img;
+  return NULL;
 }
diff --git a/png.c b/png.c
new file mode 100644
index 0000000..02b951a
--- /dev/null
+++ b/png.c
@@ -0,0 +1,50 @@
+#include <SDL2/SDL.h>
+#include <string.h>
+#include <png.h>
+
+SDL_Texture* imv_load_png(SDL_Renderer *r, const char* path)
+{
+  FILE *fp = fopen(path, "rb");
+
+  if(!fp) {
+    return NULL;
+  }
+
+  png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+  if(!png) {
+    fclose(fp);
+    return NULL;
+  }
+
+  png_infop info = png_create_info_struct(png);
+  if(!info) {
+    fclose(fp);
+    png_destroy_read_struct(&png, NULL, NULL);
+    return NULL;
+  }
+
+  png_init_io(png, fp);
+  png_read_png(png, info,
+      PNG_TRANSFORM_STRIP_16 | PNG_TRANSFORM_PACKING | PNG_TRANSFORM_EXPAND,
+      NULL);
+  png_uint_32 width, height;
+  png_get_IHDR(png, info, &width, &height, NULL, NULL, NULL, NULL, NULL);
+  unsigned int bytes_per_row = png_get_rowbytes(png, info);
+  png_bytepp row_ptrs = png_get_rows(png, info);
+
+  char* pixels = (char*)malloc(bytes_per_row*height);
+  for (unsigned int i = 0; i < height; i++) {
+    memcpy(pixels + bytes_per_row * i, row_ptrs[i], bytes_per_row);
+  }
+  png_destroy_read_struct(&png, &info, NULL);
+  fclose(fp);
+
+  SDL_Texture *img = SDL_CreateTexture(r,
+      SDL_PIXELFORMAT_RGB24, SDL_TEXTUREACCESS_STATIC,
+      width, height);
+
+  SDL_Rect area = {0,0,width,height};
+  SDL_UpdateTexture(img, &area, pixels, bytes_per_row);
+  free(pixels);
+  return img;
+}
-- 
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