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1706
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1 *
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2 * Routines for converting screen types.
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3 * Each routine expects a pointer in X to one line of screen data.
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4 * Data is converted in-place.
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5 *
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6 * These conversions lose no data.
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7 * MGE57: Converts type 5 line to type 7 line.
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8 * MGE67: Converts type 6 line to type 7 line.
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9 * MGE68: Converts type 6 line to type 8 line.
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10 * These conversions, of necessity, lose some data.
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11 * MGE76: Converts type 7 line to type 6 line by throwing out odd pixels
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12 * MAC75: Converts type 7 line to type 5 line by keeping hi-order bit of pixel
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13 * MAC76: Converts type 7 line to type 6 line by averaging pairs of pixels
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14 *
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15
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16 ifp1
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1777
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17 use os9defs.a
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1706
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18 endc
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19
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20 psect view_convert_a,0,0,0,0,0
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21
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22 *
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23 * Converts type 6 (320 4-color) into type 7 (640 4-color)
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24 *
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25 MGE67tab fcb $00,$05,$0a,$0f,$50,$55,$5a,$5f,$a0,$a5,$aa,$af,$f0,$f5,$fa,$ff
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26 MGE67:
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27 pshs y
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28 leay MGE67tab,pcr
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29 bsr MGEconv
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30 puls y,pc
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31
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32 *
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33 * Converts type 5 (2-color) line of data into type 7 (4-color)
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34 *
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35 MGE57tab fcb $00,$01,$04,$05,$10,$11,$14,$15,$40,$41,$44,$45,$50,$51,$54,$55
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36 MGE57:
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37 pshs y
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38 leay MGE57tab,pcr
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39 bsr MGEconv
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40 puls y,pc
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41
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42 MGE68tab fcb $00,$01,$02,$03,$10,$11,$12,$13,$20,$21,$22,$23,$30,$31,$32,$33
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43 MGE68:
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44 pshs y
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45 leay MGE68tab,pcr
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46 bsr MGEconv
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47 puls y,pc
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48
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49 MGEconv
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50 pshs a,b,x,y,u
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51 leau 80,x U pts to end of source.
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52 leax 160,x X pts to end of destination.
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53 ldb #80
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54 MGEconvloop
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55 lda ,-u
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56 anda #$0f
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57 lda a,y
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58 sta ,-x
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59 lda ,u
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60 lsra
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61 lsra
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62 lsra
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63 lsra
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64 lda a,y
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65 sta ,-x
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66 decb
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67 bne MGEconvloop
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68 puls a,b,x,y,u,pc
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69
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70 *
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71 * Throw out every other pixel to convert 640 4-color to 320 4-color
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72 MGE76table fcb $00,$10,$20,$30,$40,$50,$60,$70,$80,$90,$a0,$b0,$c0,$d0,$e0,$f0
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73 MGE76:
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74 pshs a,b,x,u,y
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75 leay MGE76table,pcr
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76 tfr x,u
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77 ldb #160
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78 pshs b
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79 MGE76loop
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80 lda 1,x
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81 anda #$0f
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82 ldb ,x++
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83 andb #$0f
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84 ora b,y
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85 sta ,u+
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86 dec ,s
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87 bne MGE76loop
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88 puls b
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89 puls a,b,x,u,y,pc
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90
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91
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92 *
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93 * Convert type 7 data to type 5 data for MAC screen.
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94 *
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95 MAC75:
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96 pshs a,b,x,y,u
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97 leau ,x
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98 ldy #160
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99 MAC75loop
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100 ldb ,x+
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101 lslb
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102 rola
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103 lslb
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104 lslb
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105 rola
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106 lslb
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107 lslb
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108 rola
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109 lslb
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110 lslb
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111 rola
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112 ldb ,x+
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113 lslb
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114 rola
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115 lslb
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116 lslb
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117 rola
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118 lslb
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119 lslb
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120 rola
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121 lslb
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122 lslb
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123 rola
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124 sta ,u+
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125 leay -1,y
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126 bne MAC75loop
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127 puls a,b,x,y,u,pc
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128
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129 * Convert type 7 to type 6 by averaging pairs of pixels.
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130 MAC76table fcb $00,$40,$40,$80,$00,$40,$80,$80,$40,$40,$80,$c0,$40,$80,$80,$c0
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131 MAC76:
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132 pshs a,b,x,y,u
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133 leau ,x
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134 leay MAC76table,pcr
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135 ldb #160
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136 pshs b
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137 MAC76loop
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138 ldb ,x
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139 lsrb
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140 lsrb
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141 lsrb
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142 lsrb
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143 ldb b,y
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144 lslb
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145 rola
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146 lslb
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147 rola
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148 ldb ,x+
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149 andb #$0f
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150 ldb b,y
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151 lslb
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152 rola
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153 lslb
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154 rola
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155 ldb ,x
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156 lsrb
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157 lsrb
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158 lsrb
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159 lsrb
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160 ldb b,y
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161 lslb
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162 rola
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163 lslb
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164 rola
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165 ldb ,x+
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166 andb #$0f
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167 ldb b,y
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168 lslb
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169 rola
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170 lslb
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171 rola
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172 sta ,u+
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173 dec ,s
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174 bne MAC76loop
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175 puls b
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176 puls a,b,x,y,u,pc
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177
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178 endsect
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