diff --git a/src/PIL/BmpImagePlugin.py b/src/PIL/BmpImagePlugin.py
index fa096b89b3c..98685be0b43 100644
--- a/src/PIL/BmpImagePlugin.py
+++ b/src/PIL/BmpImagePlugin.py
@@ -51,7 +51,7 @@ def _accept(prefix):
 
 
 def _dib_accept(prefix):
-    return i32(prefix[:4]) in [12, 40, 64, 108, 124]
+    return i32(prefix) in [12, 40, 64, 108, 124]
 
 
 # =============================================================================
@@ -86,10 +86,10 @@ def _bitmap(self, header=0, offset=0):
         # -------------------------------------------------- IBM OS/2 Bitmap v1
         # ----- This format has different offsets because of width/height types
         if file_info["header_size"] == 12:
-            file_info["width"] = i16(header_data[0:2])
-            file_info["height"] = i16(header_data[2:4])
-            file_info["planes"] = i16(header_data[4:6])
-            file_info["bits"] = i16(header_data[6:8])
+            file_info["width"] = i16(header_data, 0)
+            file_info["height"] = i16(header_data, 2)
+            file_info["planes"] = i16(header_data, 4)
+            file_info["bits"] = i16(header_data, 6)
             file_info["compression"] = self.RAW
             file_info["palette_padding"] = 3
 
@@ -98,22 +98,22 @@ def _bitmap(self, header=0, offset=0):
         elif file_info["header_size"] in (40, 64, 108, 124):
             file_info["y_flip"] = header_data[7] == 0xFF
             file_info["direction"] = 1 if file_info["y_flip"] else -1
-            file_info["width"] = i32(header_data[0:4])
+            file_info["width"] = i32(header_data, 0)
             file_info["height"] = (
-                i32(header_data[4:8])
+                i32(header_data, 4)
                 if not file_info["y_flip"]
-                else 2 ** 32 - i32(header_data[4:8])
+                else 2 ** 32 - i32(header_data, 4)
             )
-            file_info["planes"] = i16(header_data[8:10])
-            file_info["bits"] = i16(header_data[10:12])
-            file_info["compression"] = i32(header_data[12:16])
+            file_info["planes"] = i16(header_data, 8)
+            file_info["bits"] = i16(header_data, 10)
+            file_info["compression"] = i32(header_data, 12)
             # byte size of pixel data
-            file_info["data_size"] = i32(header_data[16:20])
+            file_info["data_size"] = i32(header_data, 16)
             file_info["pixels_per_meter"] = (
-                i32(header_data[20:24]),
-                i32(header_data[24:28]),
+                i32(header_data, 20),
+                i32(header_data, 24),
             )
-            file_info["colors"] = i32(header_data[28:32])
+            file_info["colors"] = i32(header_data, 28)
             file_info["palette_padding"] = 4
             self.info["dpi"] = tuple(
                 int(x / 39.3701 + 0.5) for x in file_info["pixels_per_meter"]
@@ -123,7 +123,7 @@ def _bitmap(self, header=0, offset=0):
                     for idx, mask in enumerate(
                         ["r_mask", "g_mask", "b_mask", "a_mask"]
                     ):
-                        file_info[mask] = i32(header_data[36 + idx * 4 : 40 + idx * 4])
+                        file_info[mask] = i32(header_data, 36 + idx * 4)
                 else:
                     # 40 byte headers only have the three components in the
                     # bitfields masks, ref:
@@ -266,7 +266,7 @@ def _open(self):
         if not _accept(head_data):
             raise SyntaxError("Not a BMP file")
         # read the start position of the BMP image data (u32)
-        offset = i32(head_data[10:14])
+        offset = i32(head_data, 10)
         # load bitmap information (offset=raster info)
         self._bitmap(offset=offset)
 
diff --git a/src/PIL/CurImagePlugin.py b/src/PIL/CurImagePlugin.py
index 8451fe90fe4..42af5cafcef 100644
--- a/src/PIL/CurImagePlugin.py
+++ b/src/PIL/CurImagePlugin.py
@@ -47,7 +47,7 @@ def _open(self):
 
         # pick the largest cursor in the file
         m = b""
-        for i in range(i16(s[4:])):
+        for i in range(i16(s, 4)):
             s = self.fp.read(16)
             if not m:
                 m = s
@@ -57,7 +57,7 @@ def _open(self):
             raise TypeError("No cursors were found")
 
         # load as bitmap
-        self._bitmap(i32(m[12:]) + offset)
+        self._bitmap(i32(m, 12) + offset)
 
         # patch up the bitmap height
         self._size = self.size[0], self.size[1] // 2
diff --git a/src/PIL/EpsImagePlugin.py b/src/PIL/EpsImagePlugin.py
index ec2329c7e16..dc61f48edc9 100644
--- a/src/PIL/EpsImagePlugin.py
+++ b/src/PIL/EpsImagePlugin.py
@@ -312,14 +312,14 @@ def _find_offset(self, fp):
             fp.seek(0, io.SEEK_END)
             length = fp.tell()
             offset = 0
-        elif i32(s[0:4]) == 0xC6D3D0C5:
+        elif i32(s, 0) == 0xC6D3D0C5:
             # FIX for: Some EPS file not handled correctly / issue #302
             # EPS can contain binary data
             # or start directly with latin coding
             # more info see:
             # https://web.archive.org/web/20160528181353/http://partners.adobe.com/public/developer/en/ps/5002.EPSF_Spec.pdf
-            offset = i32(s[4:8])
-            length = i32(s[8:12])
+            offset = i32(s, 4)
+            length = i32(s, 8)
         else:
             raise SyntaxError("not an EPS file")
 
diff --git a/src/PIL/FliImagePlugin.py b/src/PIL/FliImagePlugin.py
index 5a324702440..f2d4857f730 100644
--- a/src/PIL/FliImagePlugin.py
+++ b/src/PIL/FliImagePlugin.py
@@ -26,7 +26,7 @@
 
 
 def _accept(prefix):
-    return len(prefix) >= 6 and i16(prefix[4:6]) in [0xAF11, 0xAF12]
+    return len(prefix) >= 6 and i16(prefix, 4) in [0xAF11, 0xAF12]
 
 
 ##
@@ -46,22 +46,22 @@ def _open(self):
         s = self.fp.read(128)
         if not (
             _accept(s)
-            and i16(s[14:16]) in [0, 3]  # flags
+            and i16(s, 14) in [0, 3]  # flags
             and s[20:22] == b"\x00\x00"  # reserved
         ):
             raise SyntaxError("not an FLI/FLC file")
 
         # frames
-        self.n_frames = i16(s[6:8])
+        self.n_frames = i16(s, 6)
         self.is_animated = self.n_frames > 1
 
         # image characteristics
         self.mode = "P"
-        self._size = i16(s[8:10]), i16(s[10:12])
+        self._size = i16(s, 8), i16(s, 10)
 
         # animation speed
-        duration = i32(s[16:20])
-        magic = i16(s[4:6])
+        duration = i32(s, 16)
+        magic = i16(s, 4)
         if magic == 0xAF11:
             duration = (duration * 1000) // 70
         self.info["duration"] = duration
@@ -73,17 +73,17 @@ def _open(self):
 
         self.__offset = 128
 
-        if i16(s[4:6]) == 0xF100:
+        if i16(s, 4) == 0xF100:
             # prefix chunk; ignore it
             self.__offset = self.__offset + i32(s)
             s = self.fp.read(16)
 
-        if i16(s[4:6]) == 0xF1FA:
+        if i16(s, 4) == 0xF1FA:
             # look for palette chunk
             s = self.fp.read(6)
-            if i16(s[4:6]) == 11:
+            if i16(s, 4) == 11:
                 self._palette(palette, 2)
-            elif i16(s[4:6]) == 4:
+            elif i16(s, 4) == 4:
                 self._palette(palette, 0)
 
         palette = [o8(r) + o8(g) + o8(b) for (r, g, b) in palette]
diff --git a/src/PIL/GbrImagePlugin.py b/src/PIL/GbrImagePlugin.py
index 5e447b4115a..0f230602db8 100644
--- a/src/PIL/GbrImagePlugin.py
+++ b/src/PIL/GbrImagePlugin.py
@@ -29,7 +29,7 @@
 
 
 def _accept(prefix):
-    return len(prefix) >= 8 and i32(prefix[:4]) >= 20 and i32(prefix[4:8]) in (1, 2)
+    return len(prefix) >= 8 and i32(prefix, 0) >= 20 and i32(prefix, 4) in (1, 2)
 
 
 ##
diff --git a/src/PIL/GdImageFile.py b/src/PIL/GdImageFile.py
index 986dd063e17..9c34adaa6c4 100644
--- a/src/PIL/GdImageFile.py
+++ b/src/PIL/GdImageFile.py
@@ -48,17 +48,17 @@ def _open(self):
         # Header
         s = self.fp.read(1037)
 
-        if not i16(s[:2]) in [65534, 65535]:
+        if not i16(s) in [65534, 65535]:
             raise SyntaxError("Not a valid GD 2.x .gd file")
 
         self.mode = "L"  # FIXME: "P"
-        self._size = i16(s[2:4]), i16(s[4:6])
+        self._size = i16(s, 2), i16(s, 4)
 
         trueColor = s[6]
         trueColorOffset = 2 if trueColor else 0
 
         # transparency index
-        tindex = i32(s[7 + trueColorOffset : 7 + trueColorOffset + 4])
+        tindex = i32(s, 7 + trueColorOffset)
         if tindex < 256:
             self.info["transparency"] = tindex
 
diff --git a/src/PIL/GifImagePlugin.py b/src/PIL/GifImagePlugin.py
index 1873e441f4d..7c083bd8bd2 100644
--- a/src/PIL/GifImagePlugin.py
+++ b/src/PIL/GifImagePlugin.py
@@ -69,7 +69,7 @@ def _open(self):
             raise SyntaxError("not a GIF file")
 
         self.info["version"] = s[:6]
-        self._size = i16(s[6:]), i16(s[8:])
+        self._size = i16(s, 6), i16(s, 8)
         self.tile = []
         flags = s[10]
         bits = (flags & 7) + 1
@@ -193,7 +193,7 @@ def _seek(self, frame):
                     flags = block[0]
                     if flags & 1:
                         info["transparency"] = block[3]
-                    info["duration"] = i16(block[1:3]) * 10
+                    info["duration"] = i16(block, 1) * 10
 
                     # disposal method - find the value of bits 4 - 6
                     dispose_bits = 0b00011100 & flags
@@ -223,7 +223,7 @@ def _seek(self, frame):
                     if block[:11] == b"NETSCAPE2.0":
                         block = self.data()
                         if len(block) >= 3 and block[0] == 1:
-                            info["loop"] = i16(block[1:3])
+                            info["loop"] = i16(block, 1)
                 while self.data():
                     pass
 
@@ -234,8 +234,8 @@ def _seek(self, frame):
                 s = self.fp.read(9)
 
                 # extent
-                x0, y0 = i16(s[0:]), i16(s[2:])
-                x1, y1 = x0 + i16(s[4:]), y0 + i16(s[6:])
+                x0, y0 = i16(s, 0), i16(s, 2)
+                x1, y1 = x0 + i16(s, 4), y0 + i16(s, 6)
                 if x1 > self.size[0] or y1 > self.size[1]:
                     self._size = max(x1, self.size[0]), max(y1, self.size[1])
                 self.dispose_extent = x0, y0, x1, y1
diff --git a/src/PIL/IcoImagePlugin.py b/src/PIL/IcoImagePlugin.py
index 7dff008edf1..e1bfa7a5987 100644
--- a/src/PIL/IcoImagePlugin.py
+++ b/src/PIL/IcoImagePlugin.py
@@ -102,7 +102,7 @@ def __init__(self, buf):
         self.entry = []
 
         # Number of items in file
-        self.nb_items = i16(s[4:])
+        self.nb_items = i16(s, 4)
 
         # Get headers for each item
         for i in range(self.nb_items):
@@ -113,10 +113,10 @@ def __init__(self, buf):
                 "height": s[1],
                 "nb_color": s[2],  # No. of colors in image (0 if >=8bpp)
                 "reserved": s[3],
-                "planes": i16(s[4:]),
-                "bpp": i16(s[6:]),
-                "size": i32(s[8:]),
-                "offset": i32(s[12:]),
+                "planes": i16(s, 4),
+                "bpp": i16(s, 6),
+                "size": i32(s, 8),
+                "offset": i32(s, 12),
             }
 
             # See Wikipedia
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 815c0f65963..e2540a2b2e5 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -3374,7 +3374,7 @@ def get_ifd(self, tag):
 
                 if self[0x927C][:8] == b"FUJIFILM":
                     exif_data = self[0x927C]
-                    ifd_offset = i32le(exif_data[8:12])
+                    ifd_offset = i32le(exif_data, 8)
                     ifd_data = exif_data[ifd_offset:]
 
                     makernote = {}
diff --git a/src/PIL/IptcImagePlugin.py b/src/PIL/IptcImagePlugin.py
index 932601adc25..0bbe50668d8 100644
--- a/src/PIL/IptcImagePlugin.py
+++ b/src/PIL/IptcImagePlugin.py
@@ -77,7 +77,7 @@ def field(self):
         elif size > 128:
             size = i(self.fp.read(size - 128))
         else:
-            size = i16(s[3:])
+            size = i16(s, 3)
 
         return tag, size
 
diff --git a/src/PIL/JpegImagePlugin.py b/src/PIL/JpegImagePlugin.py
index be917e01e56..054495e6f6a 100644
--- a/src/PIL/JpegImagePlugin.py
+++ b/src/PIL/JpegImagePlugin.py
@@ -124,10 +124,10 @@ def APP(self, marker):
                 data = s[offset : offset + size]
                 if code == 0x03ED:  # ResolutionInfo
                     data = {
-                        "XResolution": i32(data[:4]) / 65536,
-                        "DisplayedUnitsX": i16(data[4:8]),
-                        "YResolution": i32(data[8:12]) / 65536,
-                        "DisplayedUnitsY": i16(data[12:]),
+                        "XResolution": i32(data, 0) / 65536,
+                        "DisplayedUnitsX": i16(data, 4),
+                        "YResolution": i32(data, 8) / 65536,
+                        "DisplayedUnitsY": i16(data, 12),
                     }
                 photoshop[code] = data
                 offset += size
@@ -194,7 +194,7 @@ def SOF(self, marker):
 
     n = i16(self.fp.read(2)) - 2
     s = ImageFile._safe_read(self.fp, n)
-    self._size = i16(s[3:]), i16(s[1:])
+    self._size = i16(s, 3), i16(s, 1)
 
     self.bits = s[0]
     if self.bits != 8:
diff --git a/src/PIL/MspImagePlugin.py b/src/PIL/MspImagePlugin.py
index 95190a9443e..e1fdc1fdf75 100644
--- a/src/PIL/MspImagePlugin.py
+++ b/src/PIL/MspImagePlugin.py
@@ -58,12 +58,12 @@ def _open(self):
         # Header checksum
         checksum = 0
         for i in range(0, 32, 2):
-            checksum = checksum ^ i16(s[i : i + 2])
+            checksum = checksum ^ i16(s, i)
         if checksum != 0:
             raise SyntaxError("bad MSP checksum")
 
         self.mode = "1"
-        self._size = i16(s[4:]), i16(s[6:])
+        self._size = i16(s, 4), i16(s, 6)
 
         if s[:4] == b"DanM":
             self.tile = [("raw", (0, 0) + self.size, 32, ("1", 0, 1))]
diff --git a/src/PIL/PixarImagePlugin.py b/src/PIL/PixarImagePlugin.py
index 91f0314b515..c4860b6c4f3 100644
--- a/src/PIL/PixarImagePlugin.py
+++ b/src/PIL/PixarImagePlugin.py
@@ -49,10 +49,10 @@ def _open(self):
         # read rest of header
         s = s + self.fp.read(508)
 
-        self._size = i16(s[418:420]), i16(s[416:418])
+        self._size = i16(s, 418), i16(s, 416)
 
         # get channel/depth descriptions
-        mode = i16(s[424:426]), i16(s[426:428])
+        mode = i16(s, 424), i16(s, 426)
 
         if mode == (14, 2):
             self.mode = "RGB"
diff --git a/src/PIL/PngImagePlugin.py b/src/PIL/PngImagePlugin.py
index fd7ef712f8f..10e6010ebe4 100644
--- a/src/PIL/PngImagePlugin.py
+++ b/src/PIL/PngImagePlugin.py
@@ -409,7 +409,7 @@ def chunk_IHDR(self, pos, length):
 
         # image header
         s = ImageFile._safe_read(self.fp, length)
-        self.im_size = i32(s), i32(s[4:])
+        self.im_size = i32(s, 0), i32(s, 4)
         try:
             self.im_mode, self.im_rawmode = _MODES[(s[8], s[9])]
         except Exception:
@@ -464,7 +464,7 @@ def chunk_tRNS(self, pos, length):
         elif self.im_mode in ("1", "L", "I"):
             self.im_info["transparency"] = i16(s)
         elif self.im_mode == "RGB":
-            self.im_info["transparency"] = i16(s), i16(s[2:]), i16(s[4:])
+            self.im_info["transparency"] = i16(s), i16(s, 2), i16(s, 4)
         return s
 
     def chunk_gAMA(self, pos, length):
@@ -497,7 +497,7 @@ def chunk_pHYs(self, pos, length):
 
         # pixels per unit
         s = ImageFile._safe_read(self.fp, length)
-        px, py = i32(s), i32(s[4:])
+        px, py = i32(s, 0), i32(s, 4)
         unit = s[8]
         if unit == 1:  # meter
             dpi = int(px * 0.0254 + 0.5), int(py * 0.0254 + 0.5)
@@ -618,7 +618,7 @@ def chunk_acTL(self, pos, length):
             warnings.warn("Invalid APNG, will use default PNG image if possible")
             return s
         self.im_n_frames = n_frames
-        self.im_info["loop"] = i32(s[4:])
+        self.im_info["loop"] = i32(s, 4)
         self.im_custom_mimetype = "image/apng"
         return s
 
@@ -630,13 +630,13 @@ def chunk_fcTL(self, pos, length):
         ):
             raise SyntaxError("APNG contains frame sequence errors")
         self._seq_num = seq
-        width, height = i32(s[4:]), i32(s[8:])
-        px, py = i32(s[12:]), i32(s[16:])
+        width, height = i32(s, 4), i32(s, 8)
+        px, py = i32(s, 12), i32(s, 16)
         im_w, im_h = self.im_size
         if px + width > im_w or py + height > im_h:
             raise SyntaxError("APNG contains invalid frames")
         self.im_info["bbox"] = (px, py, px + width, py + height)
-        delay_num, delay_den = i16(s[20:]), i16(s[22:])
+        delay_num, delay_den = i16(s, 20), i16(s, 22)
         if delay_den == 0:
             delay_den = 100
         self.im_info["duration"] = float(delay_num) / float(delay_den) * 1000
diff --git a/src/PIL/PsdImagePlugin.py b/src/PIL/PsdImagePlugin.py
index 8d1dbf2b2e8..d3799edc3d9 100644
--- a/src/PIL/PsdImagePlugin.py
+++ b/src/PIL/PsdImagePlugin.py
@@ -63,12 +63,12 @@ def _open(self):
         # header
 
         s = read(26)
-        if not _accept(s) or i16(s[4:]) != 1:
+        if not _accept(s) or i16(s, 4) != 1:
             raise SyntaxError("not a PSD file")
 
-        psd_bits = i16(s[22:])
-        psd_channels = i16(s[12:])
-        psd_mode = i16(s[24:])
+        psd_bits = i16(s, 22)
+        psd_channels = i16(s, 12)
+        psd_mode = i16(s, 24)
 
         mode, channels = MODES[(psd_mode, psd_bits)]
 
@@ -76,7 +76,7 @@ def _open(self):
             raise OSError("not enough channels")
 
         self.mode = mode
-        self._size = i32(s[18:]), i32(s[14:])
+        self._size = i32(s, 18), i32(s, 14)
 
         #
         # color mode data
@@ -291,7 +291,7 @@ def _maketile(file, mode, bbox, channels):
                 layer += ";I"
             tile.append(("packbits", bbox, offset, layer))
             for y in range(ysize):
-                offset = offset + i16(bytecount[i : i + 2])
+                offset = offset + i16(bytecount, i)
                 i += 2
 
     file.seek(offset)
diff --git a/src/PIL/SgiImagePlugin.py b/src/PIL/SgiImagePlugin.py
index 58a62fa5d72..d0f7c99934f 100644
--- a/src/PIL/SgiImagePlugin.py
+++ b/src/PIL/SgiImagePlugin.py
@@ -69,16 +69,16 @@ def _open(self):
         bpc = s[3]
 
         # dimension : 1, 2 or 3 (depending on xsize, ysize and zsize)
-        dimension = i16(s[4:])
+        dimension = i16(s, 4)
 
         # xsize : width
-        xsize = i16(s[6:])
+        xsize = i16(s, 6)
 
         # ysize : height
-        ysize = i16(s[8:])
+        ysize = i16(s, 8)
 
         # zsize : channels count
-        zsize = i16(s[10:])
+        zsize = i16(s, 10)
 
         # layout
         layout = bpc, dimension, zsize
diff --git a/src/PIL/SunImagePlugin.py b/src/PIL/SunImagePlugin.py
index d99884293ae..c03759a01e6 100644
--- a/src/PIL/SunImagePlugin.py
+++ b/src/PIL/SunImagePlugin.py
@@ -58,13 +58,13 @@ def _open(self):
 
         offset = 32
 
-        self._size = i32(s[4:8]), i32(s[8:12])
+        self._size = i32(s, 4), i32(s, 8)
 
-        depth = i32(s[12:16])
-        # data_length = i32(s[16:20])   # unreliable, ignore.
-        file_type = i32(s[20:24])
-        palette_type = i32(s[24:28])  # 0: None, 1: RGB, 2: Raw/arbitrary
-        palette_length = i32(s[28:32])
+        depth = i32(s, 12)
+        # data_length = i32(s, 16)   # unreliable, ignore.
+        file_type = i32(s, 20)
+        palette_type = i32(s, 24)  # 0: None, 1: RGB, 2: Raw/arbitrary
+        palette_length = i32(s, 28)
 
         if depth == 1:
             self.mode, rawmode = "1", "1;I"
diff --git a/src/PIL/TgaImagePlugin.py b/src/PIL/TgaImagePlugin.py
index 2ebe5d34916..2b936d68732 100644
--- a/src/PIL/TgaImagePlugin.py
+++ b/src/PIL/TgaImagePlugin.py
@@ -64,7 +64,7 @@ def _open(self):
 
         flags = s[17]
 
-        self._size = i16(s[12:]), i16(s[14:])
+        self._size = i16(s, 12), i16(s, 14)
 
         # validate header fields
         if (
@@ -110,7 +110,7 @@ def _open(self):
 
         if colormaptype:
             # read palette
-            start, size, mapdepth = i16(s[3:]), i16(s[5:]), i16(s[7:])
+            start, size, mapdepth = i16(s, 3), i16(s, 5), i16(s, 7)
             if mapdepth == 16:
                 self.palette = ImagePalette.raw(
                     "BGR;16", b"\0" * 2 * start + self.fp.read(2 * size)