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Qu’est ce qu’une image

Qu’est ce qu’une image. Ensemble de pixels (picture element). Représentation sous forme matricielle Image = A[i,j] où 1<i<N 1<j<M  tableau de N lignes et M colonnes. Pixels codés sur 1, 8bits (256 valeurs)… Plusieurs formats d’images…. Image en Niveaux de gris. ans =

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Qu’est ce qu’une image

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  1. Qu’est ce qu’une image • Ensemble de pixels (picture element). • Représentation sous forme matricielleImage = A[i,j] où 1<i<N 1<j<M tableau de N lignes et M colonnes. • Pixels codés sur 1, 8bits (256 valeurs)… • Plusieurs formats d’images…

  2. Image en Niveaux de gris ans = 90.0688 210.2373 255.0000 229.9738 87.6085 210.2373 255.0000 255.0000 136.2158 214.0000 255.0000 255.0000 124.9384 214.0000 255.0000 255.0000

  3. Image RVB ans(:,:,1) = 66 214 255 231 82 214 255 255 140 214 255 255 123 214 255 255 ans(:,:,3) = 66 181 255 222 90 181 255 255 148 214 255 255 140 214 255 255 ans(:,:,2) = 107 214 255 231 90 214 255 255 132 214 255 255 123 214 255 255

  4. Image indexée • La valeur d’un pixel n’est pas sa couleur, elle correspond à un indice. • 1 indice = 1 couleur • Table de correspondance indices/couleurs : palette. • Sous Matlab: colormap

  5. Image indexée indices = 32 35 65 75 117 119 123 128 palette = 0.3216 0.3529 0.3529 0.2588 0.4196 0.2588 0.4824 0.4824 0.5490 0.5490 0.5176 0.5804 0.8392 0.8392 0.7098 0.8392 0.8392 0.8392 0.9059 0.9059 0.8706 1.0000 1.0000 1.0000 ans = 35 117 128 123 32 117 128 128 75 119 128 128 65 119 128 128 …

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