diff --git a/Makefile b/Makefile
index 1beef17..5b222c8 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ LDIR = /opt/local/lib/
 LIBS = -lc -lpng16
 CFLAGS = -Wall -march=native -Ofast -Wa,-q
 OUT_DIR = build
-LABS = lab1_1 lab1_2 lab1_3 lab1_4 lab1_5 lab1_6 lab1_7 lab2_1 lab2_2 lab3 lab4 lab5 lab6 lab7
+LABS = lab1_1 lab1_2 lab1_3 lab1_4 lab1_5 lab1_6 lab1_7 lab2_1 lab2_2 lab3 lab4_2 lab5 lab6 lab7
 BINS = $(addprefix $(OUT_DIR)/,${LABS})
 OBJS = $(addsuffix .o,${BINS})
 
diff --git a/README.md b/README.md
index 887f677..f8c944e 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,8 @@ Here are the programs that I wrote during the Digital Image Processing class in
     1. [Nearest-neighbor interpolation](#nearest-neighbor-interpolation-lab2_1c)
     2. [Bilinear interpolation](#bilinear-interpolation-lab2_2c)
 3. [Alpha compositing](#alpha-compositing-lab3c)
-4. [Histogram equalization](#histogram-equalization-lab4c)
+4. Intensity transformations
+    2. [Linear contrast stretching](#linear-contrast-stretching-lab4_2c)
 5. [Convolution](#convolution-lab5c)
 6. [Median filter](#median-filter-lab6c)
 7. [Segmentation](#segmentation-lab7c)
@@ -80,11 +81,11 @@ Here are the programs that I wrote during the Digital Image Processing class in
 | <ul><li>[Goldhill.png](images/Goldhill.png) as top</li><li>[Lena.png](images/Lena.png) as bottom</li><li>[Peppers.png](images/Peppers.png) as alpha channel</li></ul> | ![Output](lab3/Goldhill_Lena_Peppers_out.png) |
 
 ---
-## Histogram equalization ([lab4.c](lab4/lab4.c))
-| Input | Output (delta = 100) |
+## Linear contrast stretching ([lab4_2.c](lab4_2/lab4_2.c))
+| Input | Output (delta = 1000) |
 | ----- | ------ |
-| ![Input](images/Goldhill.png) | ![Output](lab4/Goldhill_out_100.png) |
-| ![Input](lab4/Goldhill_in_hist.png) | ![Output](lab4/Goldhill_out_100_hist.png) |
+| ![Input](images/Auto.png) | ![Output](lab4_2/Auto_out_1000.png) |
+| ![Input](lab4_2/Auto_in_hist.png) | ![Output](lab4_2/Auto_out_1000_hist.png) |
 
 ---
 ## Convolution ([lab5.c](lab5/lab5.c))
diff --git a/images/Auto.png b/images/Auto.png
new file mode 100644
index 0000000..fc9ae8d
Binary files /dev/null and b/images/Auto.png differ
diff --git a/lab4/Goldhill_in_hist.png b/lab4/Goldhill_in_hist.png
deleted file mode 100644
index f5e0686..0000000
Binary files a/lab4/Goldhill_in_hist.png and /dev/null differ
diff --git a/lab4/Goldhill_out_100.png b/lab4/Goldhill_out_100.png
deleted file mode 100644
index c244773..0000000
Binary files a/lab4/Goldhill_out_100.png and /dev/null differ
diff --git a/lab4/Goldhill_out_100_hist.png b/lab4/Goldhill_out_100_hist.png
deleted file mode 100644
index 57cead8..0000000
Binary files a/lab4/Goldhill_out_100_hist.png and /dev/null differ
diff --git a/lab4_2/Auto_in_hist.png b/lab4_2/Auto_in_hist.png
new file mode 100644
index 0000000..a52f4b7
Binary files /dev/null and b/lab4_2/Auto_in_hist.png differ
diff --git a/lab4_2/Auto_out_1000.png b/lab4_2/Auto_out_1000.png
new file mode 100644
index 0000000..19734ec
Binary files /dev/null and b/lab4_2/Auto_out_1000.png differ
diff --git a/lab4_2/Auto_out_1000_hist.png b/lab4_2/Auto_out_1000_hist.png
new file mode 100644
index 0000000..2e9e6b2
Binary files /dev/null and b/lab4_2/Auto_out_1000_hist.png differ
diff --git a/lab4/lab4.c b/lab4_2/lab4_2.c
similarity index 100%
rename from lab4/lab4.c
rename to lab4_2/lab4_2.c