问题是您的图像已泛化。因此，没有为每个像素存储完整的RGB三元组，而是有一个256个RGB三元组的列表，然后在每个像素位置将索引存储到列表中-
这样可以节省空间。
我认为您需要这样做：
#!/usr/local/bin/python3import numpy as npfrom PIL import Imageimport matplotlib.pyplot as plt#%matplotlib inlineimg = Image.open('cycle.png').convert('RGB').convert('L')img.show()arr = np.array(img)plt.imshow(arr, cmap='gray')响应您在评论中的进一步问题，是的，调色板条目255表示
E0E0C0。我在终端中使用以下命令使用 ImageMagick
进行了显示，以显示图像详细信息并转储调色板。请参阅下面的列表行：
identify -verbose cycle.pngImage: cycle.png Format: PNG (Portable Network Graphics) Mime type: image/png Class: PseudoClass Geometry: 334x500+0+0 Units: Undefined Colorspace: sRGB Type: Palette base type: Undefined Endianess: Undefined Depth: 8-bit Channel depth: Red: 8-bit Green: 8-bit Blue: 8-bit Channel statistics: Pixels: 167000 Red: min: 0 (0) max: 224 (0.878431) mean: 93.4808 (0.366591) standard deviation: 99.7578 (0.391207) kurtosis: -1.93947 skewness: 0.148046 entropy: 0.854702 Green: min: 0 (0) max: 224 (0.878431) mean: 96.2489 (0.377447) standard deviation: 72.6758 (0.285003) kurtosis: -0.989098 skewness: -0.146725 entropy: 0.837577 Blue: min: 0 (0) max: 192 (0.752941) mean: 66.7367 (0.261712) standard deviation: 73.2147 (0.287116) kurtosis: -1.56751 skewness: 0.331185 entropy: 0.854702 Image statistics: Overall: min: 0 (0) max: 224 (0.878431) mean: 85.4888 (0.33525) standard deviation: 81.8828 (0.321109) kurtosis: -1.56309 skewness: 0.182395 entropy: 0.848994 Colors: 4 Histogram: 54389: ( 0, 0, 0) #000000 black 34183: ( 0,128, 0) #008000 green 61143: (192,128,128) #C08080 srgb(192,128,128) 17285: (224,224,192) #E0E0C0 srgb(224,224,192) Colormap entries: 256 Colormap: 0: ( 0, 0, 0,255) #000000FF black 1: (128, 0, 0,255) #800000FF maroon 2: ( 0,128, 0,255) #008000FF green 3: (128,128, 0,255) #808000FF olive 4: ( 0, 0,128,255) #000080FF navy 5: (128, 0,128,255) #800080FF purple 6: ( 0,128,128,255) #008080FF teal 7: (128,128,128,255) #808080FF fractal 8: ( 64, 0, 0,255) #400000FF srgba(64,0,0,1) 9: (192, 0, 0,255) #C00000FF srgba(192,0,0,1) 10: ( 64,128, 0,255) #408000FF srgba(64,128,0,1) 11: (192,128, 0,255) #C08000FF srgba(192,128,0,1) 12: ( 64, 0,128,255) #400080FF srgba(64,0,128,1) 13: (192, 0,128,255) #C00080FF srgba(192,0,128,1) 14: ( 64,128,128,255) #408080FF srgba(64,128,128,1) 15: (192,128,128,255) #C08080FF srgba(192,128,128,1) 16: ( 0, 64, 0,255) #004000FF srgba(0,64,0,1) 17: (128, 64, 0,255) #804000FF srgba(128,64,0,1) 18: ( 0,192, 0,255) #00C000FF srgba(0,192,0,1) 19: (128,192, 0,255) #80C000FF srgba(128,192,0,1) 20: ( 0, 64,128,255) #004080FF srgba(0,64,128,1) 21: (128, 64,128,255) #804080FF srgba(128,64,128,1) 22: ( 0,192,128,255) #00C080FF srgba(0,192,128,1) 23: (128,192,128,255) #80C080FF srgba(128,192,128,1) 24: ( 64, 64, 0,255) #404000FF srgba(64,64,0,1) 25: (192, 64, 0,255) #C04000FF srgba(192,64,0,1) 26: ( 64,192, 0,255) #40C000FF srgba(64,192,0,1) 27: (192,192, 0,255) #C0C000FF srgba(192,192,0,1) 28: ( 64, 64,128,255) #404080FF srgba(64,64,128,1) 29: (192, 64,128,255) #C04080FF srgba(192,64,128,1) 30: ( 64,192,128,255) #40C080FF srgba(64,192,128,1) 31: (192,192,128,255) #C0C080FF srgba(192,192,128,1) 32: ( 0, 0, 64,255) #000040FF srgba(0,0,64,1) 33: (128, 0, 64,255) #800040FF srgba(128,0,64,1) 34: ( 0,128, 64,255) #008040FF srgba(0,128,64,1) 35: (128,128, 64,255) #808040FF srgba(128,128,64,1) 36: ( 0, 0,192,255) #0000C0FF srgba(0,0,192,1) 37: (128, 0,192,255) #8000C0FF srgba(128,0,192,1) 38: ( 0,128,192,255) #0080C0FF srgba(0,128,192,1) 39: (128,128,192,255) #8080C0FF srgba(128,128,192,1) 40: ( 64, 0, 64,255) #400040FF srgba(64,0,64,1) 41: (192, 0, 64,255) #C00040FF srgba(192,0,64,1) 42: ( 64,128, 64,255) #408040FF srgba(64,128,64,1) 43: (192,128, 64,255) #C08040FF srgba(192,128,64,1) 44: ( 64, 0,192,255) #4000C0FF srgba(64,0,192,1) 45: (192, 0,192,255) #C000C0FF srgba(192,0,192,1) 46: ( 64,128,192,255) #4080C0FF srgba(64,128,192,1) 47: (192,128,192,255) #C080C0FF srgba(192,128,192,1) 48: ( 0, 64, 64,255) #004040FF srgba(0,64,64,1) 49: (128, 64, 64,255) #804040FF srgba(128,64,64,1) 50: ( 0,192, 64,255) #00C040FF srgba(0,192,64,1) 51: (128,192, 64,255) #80C040FF srgba(128,192,64,1) 52: ( 0, 64,192,255) #0040C0FF srgba(0,64,192,1) 53: (128, 64,192,255) #8040C0FF srgba(128,64,192,1) 54: ( 0,192,192,255) #00C0C0FF srgba(0,192,192,1) 55: (128,192,192,255) #80C0C0FF srgba(128,192,192,1) 56: ( 64, 64, 64,255) #404040FF grey25 57: (192, 64, 64,255) #C04040FF srgba(192,64,64,1) 58: ( 64,192, 64,255) #40C040FF srgba(64,192,64,1) 59: (192,192, 64,255) #C0C040FF srgba(192,192,64,1) 60: ( 64, 64,192,255) #4040C0FF srgba(64,64,192,1) 61: (192, 64,192,255) #C040C0FF srgba(192,64,192,1) 62: ( 64,192,192,255) #40C0C0FF srgba(64,192,192,1) 63: (192,192,192,255) #C0C0C0FF silver 64: ( 32, 0, 0,255) #200000FF srgba(32,0,0,1) 65: (160, 0, 0,255) #A00000FF srgba(160,0,0,1) 66: ( 32,128, 0,255) #208000FF srgba(32,128,0,1) 67: (160,128, 0,255) #A08000FF srgba(160,128,0,1) 68: ( 32, 0,128,255) #200080FF srgba(32,0,128,1) 69: (160, 0,128,255) #A00080FF srgba(160,0,128,1) 70: ( 32,128,128,255) #208080FF srgba(32,128,128,1) 71: (160,128,128,255) #A08080FF srgba(160,128,128,1) 72: ( 96, 0, 0,255) #600000FF srgba(96,0,0,1) 73: (224, 0, 0,255) #E00000FF srgba(224,0,0,1) 74: ( 96,128, 0,255) #608000FF srgba(96,128,0,1) 75: (224,128, 0,255) #E08000FF srgba(224,128,0,1) 76: ( 96, 0,128,255) #600080FF srgba(96,0,128,1) 77: (224, 0,128,255) #E00080FF srgba(224,0,128,1) 78: ( 96,128,128,255) #608080FF srgba(96,128,128,1) 79: (224,128,128,255) #E08080FF srgba(224,128,128,1) 80: ( 32, 64, 0,255) #204000FF srgba(32,64,0,1) 81: (160, 64, 0,255) #A04000FF srgba(160,64,0,1) 82: ( 32,192, 0,255) #20C000FF srgba(32,192,0,1) 83: (160,192, 0,255) #A0C000FF srgba(160,192,0,1) 84: ( 32, 64,128,255) #204080FF srgba(32,64,128,1) 85: (160, 64,128,255) #A04080FF srgba(160,64,128,1) 86: ( 32,192,128,255) #20C080FF srgba(32,192,128,1) 87: (160,192,128,255) #A0C080FF srgba(160,192,128,1) 88: ( 96, 64, 0,255) #604000FF srgba(96,64,0,1) 89: (224, 64, 0,255) #E04000FF srgba(224,64,0,1) 90: ( 96,192, 0,255) #60C000FF srgba(96,192,0,1) 91: (224,192, 0,255) #E0C000FF srgba(224,192,0,1) 92: ( 96, 64,128,255) #604080FF srgba(96,64,128,1) 93: (224, 64,128,255) #E04080FF srgba(224,64,128,1) 94: ( 96,192,128,255) #60C080FF srgba(96,192,128,1) 95: (224,192,128,255) #E0C080FF srgba(224,192,128,1) 96: ( 32, 0, 64,255) #200040FF srgba(32,0,64,1) 97: (160, 0, 64,255) #A00040FF srgba(160,0,64,1) 98: ( 32,128, 64,255) #208040FF srgba(32,128,64,1) 99: (160,128, 64,255) #A08040FF srgba(160,128,64,1) 100: ( 32, 0,192,255) #2000C0FF srgba(32,0,192,1) 101: (160, 0,192,255) #A000C0FF srgba(160,0,192,1) 102: ( 32,128,192,255) #2080C0FF srgba(32,128,192,1) 103: (160,128,192,255) #A080C0FF srgba(160,128,192,1) 104: ( 96, 0, 64,255) #600040FF srgba(96,0,64,1) 105: (224, 0, 64,255) #E00040FF srgba(224,0,64,1) 106: ( 96,128, 64,255) #608040FF srgba(96,128,64,1) 107: (224,128, 64,255) #E08040FF srgba(224,128,64,1) 108: ( 96, 0,192,255) #6000C0FF srgba(96,0,192,1) 109: (224, 0,192,255) #E000C0FF srgba(224,0,192,1) 110: ( 96,128,192,255) #6080C0FF srgba(96,128,192,1) 111: (224,128,192,255) #E080C0FF srgba(224,128,192,1) 112: ( 32, 64, 64,255) #204040FF srgba(32,64,64,1) 113: (160, 64, 64,255) #A04040FF srgba(160,64,64,1) 114: ( 32,192, 64,255) #20C040FF srgba(32,192,64,1) 115: (160,192, 64,255) #A0C040FF srgba(160,192,64,1) 116: ( 32, 64,192,255) #2040C0FF srgba(32,64,192,1) 117: (160, 64,192,255) #A040C0FF srgba(160,64,192,1) 118: ( 32,192,192,255) #20C0C0FF srgba(32,192,192,1) 119: (160,192,192,255) #A0C0C0FF srgba(160,192,192,1) 120: ( 96, 64, 64,255) #604040FF srgba(96,64,64,1) 121: (224, 64, 64,255) #E04040FF srgba(224,64,64,1) 122: ( 96,192, 64,255) #60C040FF srgba(96,192,64,1) 123: (224,192, 64,255) #E0C040FF srgba(224,192,64,1) 124: ( 96, 64,192,255) #6040C0FF srgba(96,64,192,1) 125: (224, 64,192,255) #E040C0FF srgba(224,64,192,1) 126: ( 96,192,192,255) #60C0C0FF srgba(96,192,192,1) 127: (224,192,192,255) #E0C0C0FF srgba(224,192,192,1) 128: ( 0, 32, 0,255) #002000FF srgba(0,32,0,1) 129: (128, 32, 0,255) #802000FF srgba(128,32,0,1) 130: ( 0,160, 0,255) #00A000FF srgba(0,160,0,1) 131: (128,160, 0,255) #80A000FF srgba(128,160,0,1) 132: ( 0, 32,128,255) #002080FF srgba(0,32,128,1) 133: (128, 32,128,255) #802080FF srgba(128,32,128,1) 134: ( 0,160,128,255) #00A080FF srgba(0,160,128,1) 135: (128,160,128,255) #80A080FF srgba(128,160,128,1) 136: ( 64, 32, 0,255) #402000FF srgba(64,32,0,1) 137: (192, 32, 0,255) #C02000FF srgba(192,32,0,1) 138: ( 64,160, 0,255) #40A000FF srgba(64,160,0,1) 139: (192,160, 0,255) #C0A000FF srgba(192,160,0,1) 140: ( 64, 32,128,255) #402080FF srgba(64,32,128,1) 141: (192, 32,128,255) #C02080FF srgba(192,32,128,1) 142: ( 64,160,128,255) #40A080FF srgba(64,160,128,1) 143: (192,160,128,255) #C0A080FF srgba(192,160,128,1) 144: ( 0, 96, 0,255) #006000FF srgba(0,96,0,1) 145: (128, 96, 0,255) #806000FF srgba(128,96,0,1) 146: ( 0,224, 0,255) #00E000FF srgba(0,224,0,1) 147: (128,224, 0,255) #80E000FF srgba(128,224,0,1) 148: ( 0, 96,128,255) #006080FF srgba(0,96,128,1) 149: (128, 96,128,255) #806080FF srgba(128,96,128,1) 150: ( 0,224,128,255) #00E080FF srgba(0,224,128,1) 151: (128,224,128,255) #80E080FF srgba(128,224,128,1) 152: ( 64, 96, 0,255) #406000FF srgba(64,96,0,1) 153: (192, 96, 0,255) #C06000FF srgba(192,96,0,1) 154: ( 64,224, 0,255) #40E000FF srgba(64,224,0,1) 155: (192,224, 0,255) #C0E000FF srgba(192,224,0,1) 156: ( 64, 96,128,255) #406080FF srgba(64,96,128,1) 157: (192, 96,128,255) #C06080FF srgba(192,96,128,1) 158: ( 64,224,128,255) #40E080FF srgba(64,224,128,1) 159: (192,224,128,255) #C0E080FF srgba(192,224,128,1) 160: ( 0, 32, 64,255) #002040FF srgba(0,32,64,1) 161: (128, 32, 64,255) #802040FF srgba(128,32,64,1) 162: ( 0,160, 64,255) #00A040FF srgba(0,160,64,1) 163: (128,160, 64,255) #80A040FF srgba(128,160,64,1) 164: ( 0, 32,192,255) #0020C0FF srgba(0,32,192,1) 165: (128, 32,192,255) #8020C0FF srgba(128,32,192,1) 166: ( 0,160,192,255) #00A0C0FF srgba(0,160,192,1) 167: (128,160,192,255) #80A0C0FF srgba(128,160,192,1) 168: ( 64, 32, 64,255) #402040FF srgba(64,32,64,1) 169: (192, 32, 64,255) #C02040FF srgba(192,32,64,1) 170: ( 64,160, 64,255) #40A040FF srgba(64,160,64,1) 171: (192,160, 64,255) #C0A040FF srgba(192,160,64,1) 172: ( 64, 32,192,255) #4020C0FF srgba(64,32,192,1) 173: (192, 32,192,255) #C020C0FF srgba(192,32,192,1) 174: ( 64,160,192,255) #40A0C0FF srgba(64,160,192,1) 175: (192,160,192,255) #C0A0C0FF srgba(192,160,192,1) 176: ( 0, 96, 64,255) #006040FF srgba(0,96,64,1) 177: (128, 96, 64,255) #806040FF srgba(128,96,64,1) 178: ( 0,224, 64,255) #00E040FF srgba(0,224,64,1) 179: (128,224, 64,255) #80E040FF srgba(128,224,64,1) 180: ( 0, 96,192,255) #0060C0FF srgba(0,96,192,1) 181: (128, 96,192,255) #8060C0FF srgba(128,96,192,1) 182: ( 0,224,192,255) #00E0C0FF srgba(0,224,192,1) 183: (128,224,192,255) #80E0C0FF srgba(128,224,192,1) 184: ( 64, 96, 64,255) #406040FF srgba(64,96,64,1) 185: (192, 96, 64,255) #C06040FF srgba(192,96,64,1) 186: ( 64,224, 64,255) #40E040FF srgba(64,224,64,1) 187: (192,224, 64,255) #C0E040FF srgba(192,224,64,1) 188: ( 64, 96,192,255) #4060C0FF srgba(64,96,192,1) 189: (192, 96,192,255) #C060C0FF srgba(192,96,192,1) 190: ( 64,224,192,255) #40E0C0FF srgba(64,224,192,1) 191: (192,224,192,255) #C0E0C0FF srgba(192,224,192,1) 192: ( 32, 32, 0,255) #202000FF srgba(32,32,0,1) 193: (160, 32, 0,255) #A02000FF srgba(160,32,0,1) 194: ( 32,160, 0,255) #20A000FF srgba(32,160,0,1) 195: (160,160, 0,255) #A0A000FF srgba(160,160,0,1) 196: ( 32, 32,128,255) #202080FF srgba(32,32,128,1) 197: (160, 32,128,255) #A02080FF srgba(160,32,128,1) 198: ( 32,160,128,255) #20A080FF srgba(32,160,128,1) 199: (160,160,128,255) #A0A080FF srgba(160,160,128,1) 200: ( 96, 32, 0,255) #602000FF srgba(96,32,0,1) 201: (224, 32, 0,255) #E02000FF srgba(224,32,0,1) 202: ( 96,160, 0,255) #60A000FF srgba(96,160,0,1) 203: (224,160, 0,255) #E0A000FF srgba(224,160,0,1) 204: ( 96, 32,128,255) #602080FF srgba(96,32,128,1) 205: (224, 32,128,255) #E02080FF srgba(224,32,128,1) 206: ( 96,160,128,255) #60A080FF srgba(96,160,128,1) 207: (224,160,128,255) #E0A080FF srgba(224,160,128,1) 208: ( 32, 96, 0,255) #206000FF srgba(32,96,0,1) 209: (160, 96, 0,255) #A06000FF srgba(160,96,0,1) 210: ( 32,224, 0,255) #20E000FF srgba(32,224,0,1) 211: (160,224, 0,255) #A0E000FF srgba(160,224,0,1) 212: ( 32, 96,128,255) #206080FF srgba(32,96,128,1) 213: (160, 96,128,255) #A06080FF srgba(160,96,128,1) 214: ( 32,224,128,255) #20E080FF srgba(32,224,128,1) 215: (160,224,128,255) #A0E080FF srgba(160,224,128,1) 216: ( 96, 96, 0,255) #606000FF srgba(96,96,0,1) 217: (224, 96, 0,255) #E06000FF srgba(224,96,0,1) 218: ( 96,224, 0,255) #60E000FF srgba(96,224,0,1) 219: (224,224, 0,255) #E0E000FF srgba(224,224,0,1) 220: ( 96, 96,128,255) #606080FF srgba(96,96,128,1) 221: (224, 96,128,255) #E06080FF srgba(224,96,128,1) 222: ( 96,224,128,255) #60E080FF srgba(96,224,128,1) 223: (224,224,128,255) #E0E080FF srgba(224,224,128,1) 224: ( 32, 32, 64,255) #202040FF srgba(32,32,64,1) 225: (160, 32, 64,255) #A02040FF srgba(160,32,64,1) 226: ( 32,160, 64,255) #20A040FF srgba(32,160,64,1) 227: (160,160, 64,255) #A0A040FF srgba(160,160,64,1) 228: ( 32, 32,192,255) #2020C0FF srgba(32,32,192,1) 229: (160, 32,192,255) #A020C0FF srgba(160,32,192,1) 230: ( 32,160,192,255) #20A0C0FF srgba(32,160,192,1) 231: (160,160,192,255) #A0A0C0FF srgba(160,160,192,1) 232: ( 96, 32, 64,255) #602040FF srgba(96,32,64,1) 233: (224, 32, 64,255) #E02040FF srgba(224,32,64,1) 234: ( 96,160, 64,255) #60A040FF srgba(96,160,64,1) 235: (224,160, 64,255) #E0A040FF srgba(224,160,64,1) 236: ( 96, 32,192,255) #6020C0FF srgba(96,32,192,1) 237: (224, 32,192,255) #E020C0FF srgba(224,32,192,1) 238: ( 96,160,192,255) #60A0C0FF srgba(96,160,192,1) 239: (224,160,192,255) #E0A0C0FF srgba(224,160,192,1) 240: ( 32, 96, 64,255) #206040FF srgba(32,96,64,1) 241: (160, 96, 64,255) #A06040FF srgba(160,96,64,1) 242: ( 32,224, 64,255) #20E040FF srgba(32,224,64,1) 243: (160,224, 64,255) #A0E040FF srgba(160,224,64,1) 244: ( 32, 96,192,255) #2060C0FF srgba(32,96,192,1) 245: (160, 96,192,255) #A060C0FF srgba(160,96,192,1) 246: ( 32,224,192,255) #20E0C0FF srgba(32,224,192,1) 247: (160,224,192,255) #A0E0C0FF srgba(160,224,192,1) 248: ( 96, 96, 64,255) #606040FF srgba(96,96,64,1) 249: (224, 96, 64,255) #E06040FF srgba(224,96,64,1) 250: ( 96,224, 64,255) #60E040FF srgba(96,224,64,1) 251: (224,224, 64,255) #E0E040FF srgba(224,224,64,1) 252: ( 96, 96,192,255) #6060C0FF srgba(96,96,192,1) 253: (224, 96,192,255) #E060C0FF srgba(224,96,192,1) 254: ( 96,224,192,255) #60E0C0FF srgba(96,224,192,1) 255: (224,224,192,255) #E0E0C0FF srgba(224,224,192,1) <--- THIS LINE
