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--- blog:x68_launcher_3 [2020/09/07 11:15] – [bmp.c / bmp.h] john
+++ blog:x68_launcher_3 [2020/09/07 11:51] (current) – john
@@ Line 2: / Line 2: @@
 ==== bmp.c / bmp.h ====
+   * https://github.com/megatron-uk/x68klauncher/blob/master/src/bmp.c
+   * https://github.com/megatron-uk/x68klauncher/blob/master/src/bmp.h
 The header includes these common files:
@@ Line 108: / Line 111: @@
 </code>
-The bitmap library has a single function, __bmp_ReadImage()__, that is called in several different ways to parse BMP headers, read pixel data
+The bitmap library has a single function, __bmp_ReadImage()__, that is called in several different ways to parse BMP headers and subsequently read pixel data.
+The reason the function is called in two passes is to ensure that when the header data is retrieved the image does not exceeded any specific size:
+   * Open file
+   * Read BMP header
+   * Check BMP is correct pixel depth and size
+   * Read pixel data
+<code "C">
+FILE *f;
+int status;
+f = fopen("bitmap.bmp", "rb");
+if (f == NULL){
+   return -1;
+}
+bmp = (bmpdata_t *) malloc(sizeof(bmpdata_t));
+bmp->pixels = NULL;
+status = bmp_ReadImageHeader(f, bmp);
+if (status != 0){
+   fclose(f);
+   return -1;
+}
+if (bmp->width > 200){
+  printf("Error, image is more than 200 pixels wide!\n");
+} else (
+  printf("Loading pixel data\n");
+  status = bmp_ReadImageData(f, bmp);
+)
+fclose(f);
+</code>
+----
+[[blog:x68_launcher_2|<< Back (#2: Filesystem tools, data scraping)]] | [[blog:x68_launcher_4|(#4: Graphics hardware functions) Next >>]]