Add README.

Makefile

@@ -1,12 +1,12 @@
-CC=clang
+CC=gcc
 CFLAGS=-Wall -Wextra -ansi -pedantic
 
-image_by_image: image_by_image.c image.o evolve.o
-	$(CC) $(CFLAGS) -o image_by_image image_by_image.c image.o evolve.o
-
 row_by_row: row_by_row.c image.o evolve.o
 	$(CC) $(CFLAGS) -o row_by_row row_by_row.c image.o evolve.o
 
+image_by_image: image_by_image.c image.o evolve.o
+	$(CC) $(CFLAGS) -o image_by_image image_by_image.c image.o evolve.o
+
 image.o: image.c image.h
 	$(CC) $(CFLAGS) -c -o image.o image.c
 

README.md

@@ -0,0 +1,44 @@
+# Procedural image generator
+
+This tiny project is a procedural image generator that starts with a random top
+row of pixels, and iteratively generates the rows below according to some rule.
+Each row depends only on the row immediately above.
+
+## Available rules
+
+1. *Primitive 1-to-1.*
+   Pixel's RGB values are jittered RGB values of the pixel above.
+   ![1](examples/example1.png)
+2. *Genetic, 2 parents.*
+   Each pixel has 2 parents: dad (above left) and mom (above right). R, G, and
+   B values are genes. Alleles are chosen randomly and independently from mom
+   or dad and jittered (think inheritance with mutation).
+   ![2](examples/example2.png)
+3. *Genetic, 3 parents.*
+   Each pixel has the pixel immediately above as third parent in addition to
+   'mom' and 'dad' from 2.
+   ![3](examples/example3.png)
+4. *Averaging, 2 parents.*
+   RGB values of pixel are averaged mom and dad's RGB values with some random
+   noise added.
+   ![4](examples/example4.png)
+5. *Averaging, asymmetric, 2 parents.*
+   Same as 2, except dad is directly above, mom is above right.
+   ![5](examples/example5.png)
+
+## Usage
+
+Clone repo, then:
+
+```bash
+make
+```
+This produces the `row_by_row` executable, which takes 4 mandatory parameters:
+`width` in pixels, `height` in pixels, `strategy` (1-5, per numbering above),
+and `filename` where the image is saved. The output is in PPM format.
+
+For example:
+
+```bash
+./row_by_row 2880 1800 2 image.ppm
+```