diff --git a/image_ref/utils.py b/image_ref/utils.py
new file mode 100644
index 0000000000000000000000000000000000000000..e22fccbf3bb0ecfc4a94c293eda01f9d8e7b964a
--- /dev/null
+++ b/image_ref/utils.py
@@ -0,0 +1,173 @@
+import fastapy
+import matplotlib.pyplot as plt
+import numpy as np
+from matplotlib_venn import venn2
+
+
+
+
+ALPHABET_UNMOD = {
+    "A": 1,
+    "C": 2,
+    "D": 3,
+    "E": 4,
+    "F": 5,
+    "G": 6,
+    "H": 7,
+    "I": 8,
+    "K": 9,
+    "L": 10,
+    "M": 11,
+    "N": 12,
+    "P": 13,
+    "Q": 14,
+    "R": 15,
+    "S": 16,
+    "T": 17,
+    "V": 18,
+    "W": 19,
+    "Y": 20,
+}
+
+
+MASSES_MONO = {
+    "A": 71.03711,
+    "C": 103.00919,
+    "D": 115.02694,
+    "E": 129.04259,
+    "F": 147.06841,
+    "G": 57.02146,
+    "H": 137.05891,
+    "I": 113.08406,
+    "K": 128.09496,
+    "L": 113.08406,
+    "M": 131.04049,
+    "N": 114.04293,
+    "P": 97.05276,
+    "Q": 128.05858,
+    "R": 156.1875,
+    "S": 87.03203,
+    "T": 101.04768,
+    "V": 99.06841,
+    "W": 186.07931,
+    "Y": 163.06333,
+}
+
+
+MASSES_AVG = {
+    "A": 71.0788,
+    "C": 103.1388,
+    "D": 115.0886,
+    "E": 129.1155,
+    "F": 147.1766,
+    "G": 57.0519,
+    "H": 137.1411,
+    "I": 113.1594,
+    "K": 128.1741,
+    "L": 113.1594,
+    "M": 131.1926,
+    "N": 114.1038,
+    "P": 97.1167,
+    "Q": 128.1307,
+    "R": 156.1875,
+    "S": 87.0782,
+    "T": 101.1051,
+    "V": 99.1326,
+    "W": 186.2132,
+    "Y": 163.1760,
+}
+
+# trypsin cut after K or R (if not followed by P)
+
+def cut(seq):
+    cuts = []
+    l = len(seq)
+    for i in range(l):
+        if seq[i] == 'R' or seq[i] == 'K':
+            if i < l - 1 and seq[i + 1] != 'P':
+                cuts.append(i + 1)
+    return cuts
+
+
+def cut_with_ind(seq, ind_list):
+    l = []
+    size = len(seq)
+    ind_list.append(size)
+
+    for i in range(len(ind_list) - 1):
+        if i == 0:
+            l.append(seq[:ind_list[i]])
+        l.append(seq[ind_list[i]:ind_list[i + 1]])
+
+    return l
+
+def digest(seq):
+    ind = cut(seq)
+    return cut_with_ind(seq, ind)
+
+def fasta_similarity(path_fasta_1, path_fasta_2):
+    list_seq_1=[]
+    list_seq_2 = []
+    for record in fastapy.parse(path_fasta_1):
+        list_seq_1.append(record.seq)
+    for record in fastapy.parse(path_fasta_2):
+        list_seq_2.append(record.seq)
+
+    set1 = set(list_seq_1)
+    set2 = set(list_seq_2)
+
+    venn2((set1, set2), ('Group1', 'Group2'))
+    plt.show()
+    plt.savefig('fasta_similarity.png')
+
+def compute_mass(seq, isotop):
+    m = 0
+    if isotop == 'mono':
+        for char in MASSES_MONO.keys():
+            m += MASSES_MONO[char] * seq.count(char)
+    if isotop == 'avg':
+        for char in MASSES_AVG.keys():
+            m += MASSES_AVG[char] * seq.count(char)
+    return m
+
+def build_ref_image(path_fasta, possible_charge, ms1_end_mz, ms1_start_mz, bin_mz, max_cycle, rt_pred):
+
+    #build peptide list
+    list_seq_1 = []
+    for record in fastapy.parse(path_fasta):
+        list_seq_1.append(record.seq)
+
+    list_peptides = []
+    for prot in list_seq_1 :
+        list_peptides.extend(digest(prot))
+
+    #compute m/z ration
+    mz_ratio={}
+    for seq in list_peptides:
+        mz_ratio['seq']=[]
+        for charge in possible_charge:
+            ratio = compute_mass(seq,'avg')/charge
+            if ms1_end_mz > ratio > ms1_start_mz:
+                mz_ratio['seq'].append(ratio)
+
+    #assocy predict rt
+    data=[]
+
+    #predict detectability (optional)
+
+    #build image
+    total_ms1_mz = ms1_end_mz - ms1_start_mz
+    n_bin_ms1 = int(total_ms1_mz // bin_mz)
+    im = np.zeros([max_cycle, n_bin_ms1])
+    max_rt = np.max(rt_pred)
+    min_rt = np.min(rt_pred)
+    total_rt = max_rt - min_rt
+    for (rt,mz_ratio) in data :
+        im[int((rt-min_rt/total_rt)*max_cycle),int(((mz_ratio-ms1_start_mz)/total_ms1_mz)*n_bin_ms1)]=1
+
+    return im
+
+if __name__ == '__main__':
+    # fasta_similarity('fasta/uniprotkb_proteome_UP000742934_2025_03_12.fasta','fasta/uniprotkb_proteome_UP001182277_2025_03_12.fasta')
+    # mass = build_ref_image('fasta/uniprotkb_proteome_UP000742934_2025_03_12.fasta')
+    pass
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