From c84f59058725ca2835bba5450155dffc41e80870 Mon Sep 17 00:00:00 2001
From: fredrikr79 <fredrikrobertsen7@gmail.com>
Date: Sat, 23 Aug 2025 22:43:36 +0200
Subject: [PATCH] ex0: initial

---
 exercise0/bitmap.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++
 exercise0/bitmap.h | 10 ++++++++
 exercise0/main.c   | 22 ++++++++++++++++
 3 files changed, 95 insertions(+)
 create mode 100644 exercise0/bitmap.c
 create mode 100644 exercise0/bitmap.h
 create mode 100644 exercise0/main.c

diff --git a/exercise0/bitmap.c b/exercise0/bitmap.c
new file mode 100644
index 0000000..1ae2548
--- /dev/null
+++ b/exercise0/bitmap.c
@@ -0,0 +1,63 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "bitmap.h"
+
+
+
+
+
+
+// save 24-bits bmp file, buffer must be in bmp format: upside-down
+void savebmp(char *name, uchar *buffer, int x, int y) {
+	FILE *f=fopen(name,"wb");
+	if(!f) {
+		printf("Error writing image to disk.\n");
+		return;
+	}
+	unsigned int size=x*y*3+54;
+	uchar header[54]={'B','M',size&255,(size>>8)&255,(size>>16)&255,size>>24,0,
+                    0,0,0,54,0,0,0,40,0,0,0,x&255,x>>8,0,0,y&255,y>>8,0,0,1,0,24,0,0,0,0,0,0,
+                    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
+	fwrite(header,1,54,f);
+	fwrite(buffer,1,x*y*3,f);
+	fclose(f);
+}
+
+
+// read bmp file and store image in contiguous array
+void readbmp(char* filename, uchar* array) {
+	FILE* img = fopen(filename, "rb");   //read the file
+	uchar header[54];
+	size_t result = fread(header, sizeof(uchar), 54, img); // read the 54-byte header
+
+	if (result != 54)
+	{
+		perror("Error reading file.\n");
+		return;
+	}
+
+  // extract image height and width from header
+	int width = *(int*)&header[18];
+	int height = *(int*)&header[22];
+	int padding=0;
+	while ((width*3+padding) % 4!=0) padding++;
+
+	int widthnew=width*3+padding;
+	uchar* data = calloc(widthnew, sizeof(uchar));
+
+	for (int i=0; i<height; i++ ) {
+		result = fread( data, sizeof(uchar), widthnew, img);
+
+		if (result != (size_t) widthnew)
+		{
+			perror("Error reading file.\n");
+		}
+
+		for (int j=0; j<width*3; j+=3) {
+			array[3 * i * width + j + 0] = data[j+0];
+			array[3 * i * width + j + 1] = data[j+1];
+			array[3 * i * width + j + 2] = data[j+2];
+		}
+	}
+	fclose(img); //close the file
+}
diff --git a/exercise0/bitmap.h b/exercise0/bitmap.h
new file mode 100644
index 0000000..9e78b55
--- /dev/null
+++ b/exercise0/bitmap.h
@@ -0,0 +1,10 @@
+#ifndef BITMAP_H
+#define BITMAP_H
+
+
+typedef unsigned char uchar;
+
+void savebmp(char *name, uchar *buffer, int x, int y);
+void readbmp(char *filename, uchar *array);
+
+#endif
diff --git a/exercise0/main.c b/exercise0/main.c
new file mode 100644
index 0000000..1ff4a67
--- /dev/null
+++ b/exercise0/main.c
@@ -0,0 +1,22 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "bitmap.h"
+
+#define XSIZE 2560 // Size of before image
+#define YSIZE 2048
+
+
+
+int main(void)
+{
+	uchar *image = calloc(XSIZE * YSIZE * 3, 1); // Three uchars per pixel (RGB)
+	readbmp("before.bmp", image);
+
+	// Alter the image here
+	;
+
+	savebmp("after.bmp", image, XSIZE, YSIZE);
+
+	free(image);
+	return 0;
+}