83 lines
3 KiB
Mathematica
83 lines
3 KiB
Mathematica
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% TP Codages JPEG et MPEG-2 - 3SN-M - 2022
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%--------------------------------------------------------------------------
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% Fonction de quantification (directe et inverse) des coefficients DCT
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%--------------------------------------------------------------------------
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% I_Quant = QuantificationDCT(sens,I_DCT,canal,F_Qualite,taille_bloc)
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%
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% sorties : I_Quant = image quantifiee
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%
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% entrees : sens = sens de la quantification : 'Direct' ou 'Inverse'
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% I_DCT = image avant la quantification
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% canal = canal pour le choix de la table de quantification :
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% 'Luminance', 'Chrominance' ou 'Residu'
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% F_Qualite = facteur de qualite pour la compression
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% taille_bloc = taille des blocs pour la DCT (ici 8x8)
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%--------------------------------------------------------------------------
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function I_Quant = QuantificationDCT(sens, I, canal, F_Qualite, taille_bloc)
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T = ChoixTableQuantification(canal, F_Qualite);
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if sens == "Direct"
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fun = @(block_struct) round( block_struct.data ./ T );
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elseif sens == "Inverse"
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fun = @(block_struct) round( block_struct.data .* T );
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end
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I_Quant = blockproc(I, [taille_bloc taille_bloc], fun);
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end
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%--------------------------------------------------------------------------
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% Fonction de selection d'une table de quatification JPEG en fonction du
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% type de canal et du facteur de qualite
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%--------------------------------------------------------------------------
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% T_Quant = ChoixTableQuantification(Canal, F_Qualite)
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%
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% sortie : T_Quant = Table de quantification JPEG
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%
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% entrees : canal = 'Luminance' ou 'Chrominance' (tables differentes)
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% F_Qualite = facteur de qualite (entre 0 et 97)
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%--------------------------------------------------------------------------
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function T_Quant = ChoixTableQuantification(canal,F_Qualite)
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if canal == "Luminance"
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T50 = [
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16 11 10 16 24 40 51 61;
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12 12 14 19 26 58 60 55;
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14 13 16 24 40 57 69 56;
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14 17 22 29 51 87 80 62;
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18 22 37 56 68 109 103 77;
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24 35 55 64 81 104 113 92;
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49 64 78 87 103 121 120 101;
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72 92 95 98 112 100 103 99
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];
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elseif canal == "Chrominance"
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T50 = [
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17 18 24 47 99 99 99 99 ;
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18 21 26 66 99 99 99 99 ;
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24 26 56 99 99 99 99 99 ;
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47 66 99 99 99 99 99 99 ;
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99 99 99 99 99 99 99 99 ;
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99 99 99 99 99 99 99 99 ;
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99 99 99 99 99 99 99 99 ;
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99 99 99 99 99 99 99 99
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];
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elseif canal == "Residu"
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T50 = ones(8, 8) * 16;
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end
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if F_Qualite > 50
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T_Quant = (100 - F_Qualite) * T50 / 50;
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elseif F_Qualite < 50
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T_Quant = 50 * T50 / F_Qualite;
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else
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T_Quant = T50;
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end
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T_Quant = round(T_Quant);
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end
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