2 ZSoft PCX File Format Technical Reference Manual
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7 Image File (.PCX) Format 3
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8 ZSoft .PCX FILE HEADER FORMAT 4
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9 Decoding .PCX Files 6
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10 Palette Information Description 7
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11 EGA/VGA 16 Color Palette Information 7
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12 VGA 256 Color Palette Information 7
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13 24-Bit .PCX Files 8
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14 CGA Color Palette Information 8
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16 PC Paintbrush Bitmap Character Format 9
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17 Sample "C" Routines 10
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18 FRIEZE Technical Information 14
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19 General FRIEZE Information 14
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20 7.00 and Later FRIEZE 14
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21 FRIEZE Function Calls 15
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22 FRIEZE Error Codes 18
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30 This booklet was designed to aid developers and users in understanding
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31 the technical aspects of the .PCX file format and the use of FRIEZE.
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32 Any comments, questions or suggestions about this booklet should be
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37 ATTN: Code Librarian
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38 450 Franklin Rd. Suite 100
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43 Technical Reference Manual information compiled by:
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49 To down load additional information and the source for a complete
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50 Turbo Pascal program to show .PCX files on a CGA/EGA/VGA graphics
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51 display, call our BBS at (404)427-1045. You may use a 9600 baud
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52 modem or a 2400 baud standard modem. Your modem should be set for
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53 8 data bits, 1 stop bit, and NO parity.
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55 Image File (.PCX) Format
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57 If you have technical questions on the format, please do not call
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58 technical support. ZSoft provides this document as a courtesy to
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59 its users and developers. It is not the function of Technical Support
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60 to provide programming assistance. If something is not clear, leave a
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61 message on our BBS, Compuserve, or write us a letter at the above address.
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63 The information in this section will be useful if you want to write a
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64 program to read or write PCX files (images). If you want to write a
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65 special case program for one particular image format you should be able
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66 to produce something that runs twice as fast as "Load from..." in
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69 Image files used by PC Paintbrush product family and FRIEZE (those with a
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70 .PCX extension) begin with a 128 byte header. Usually you can ignore this
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71 header, since your images will probably all have the same resolution. If
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72 you want to process different resolutions or colors, you will need to
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73 interpret the header correctly. The remainder of the image file consists
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74 of encoded graphic data. The encoding method is a simple byte oriented
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75 run-length technique. We reserve the right to change this method to
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76 improve space efficiency. When more than one color plane is stored in
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77 the file, each line of the image is stored by color plane (generally ordered
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78 red, green, blue, intensity), As shown below.
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80 Scan line 0: RRR... (Plane 0)
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89 The encoding method is:
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90 FOR each byte, X, read from the file
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91 IF the top two bits of X are 1's then
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92 count = 6 lowest bits of X
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93 data = next byte following X
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98 Since the overhead this technique requires is, on average, 25% of
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99 the non-repeating data and is at least offset whenever bytes are repeated,
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100 the file storage savings are usually considerable.
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102 ZSoft .PCX FILE HEADER FORMAT
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104 Byte Item Size Description/Comments
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105 0 Manufacturer 1 Constant Flag, 10 = ZSoft .pcx
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106 1 Version 1 Version information
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107 0 = Version 2.5 of PC Paintbrush
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108 2 = Version 2.8 w/palette information
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109 3 = Version 2.8 w/o palette information
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110 4 = PC Paintbrush for Windows(Plus for
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111 Windows uses Ver 5)
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112 5 = Version 3.0 and > of PC Paintbrush
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113 and PC Paintbrush +, includes
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114 Publisher's Paintbrush . Includes
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116 2 Encoding 1 1 = .PCX run length encoding
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117 3 BitsPerPixel 1 Number of bits to represent a pixel
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118 (per Plane) - 1, 2, 4, or 8
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119 4 Window 8 Image Dimensions: Xmin,Ymin,Xmax,Ymax
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120 12 HDpi 2 Horizontal Resolution of image in DPI*
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121 14 VDpi 2 Vertical Resolution of image in DPI*
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122 16 Colormap 48 Color palette setting, see text
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123 64 Reserved 1 Should be set to 0.
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124 65 NPlanes 1 Number of color planes
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125 66 BytesPerLine 2 Number of bytes to allocate for a scanline
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126 plane. MUST be an EVEN number. Do NOT
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127 calculate from Xmax-Xmin.
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128 68 PaletteInfo 2 How to interpret palette- 1 = Color/BW,
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129 2 = Grayscale (ignored in PB IV/ IV +)
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130 70 HscreenSize 2 Horizontal screen size in pixels. New field
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131 found only in PB IV/IV Plus
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132 72 VscreenSize 2 Vertical screen size in pixels. New field
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133 found only in PB IV/IV Plus
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134 74 Filler 54 Blank to fill out 128 byte header. Set all
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139 All sizes are measured in BYTES.
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141 All variables of SIZE 2 are integers.
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143 *HDpi and VDpi represent the Horizontal and Vertical resolutions which the
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144 image was created (either printer or scanner); i.e. an image which was
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145 scanned might have 300 and 300 in each of these fields.
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147 Decoding .PCX Files
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149 First, find the pixel dimensions of the image by calculating
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150 [XSIZE = Xmax - Xmin + 1] and [YSIZE = Ymax - Ymin + 1]. Then calculate
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151 how many bytes are required to hold one complete uncompressed scan line:
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153 TotalBytes = NPlanes * BytesPerLine
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155 Note that since there are always an even number of bytes per scan line,
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156 there will probably be unused data at the end of each scan line. TotalBytes
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157 shows how much storage must be available to decode each scan line, including
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158 any blank area on the right side of the image. You can now begin decoding
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159 the first scan line - read the first byte of data from the file. If the
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160 top two bits are set, the remaining six bits in the byte show how many times
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161 to duplicate the next byte in the file. If the top two bits are not set,
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162 the first byte is the data itself, with a count of one.
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164 Continue decoding the rest of the line. Keep a running subtotal of how
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165 many bytes are moved and duplicated into the output buffer. When the
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166 subtotal equals TotalBytes, the scan line is complete. There should always
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167 be a decoding break at the end of each scan line. But there will not be a
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168 decoding break at the end of each plane within each scan line. When the
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169 scan line is completed, there may be extra blank data at the end of each
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170 plane within the scan line. Use the XSIZE and YSIZE values to find where
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171 the valid image data is. If the data is multi-plane, BytesPerLine shows
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172 where each plane ends within the scan line.
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174 Continue decoding the remainder of the scan lines (do not just read to
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175 end-of-file). There may be additional data after the end of the image
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178 \fPalette Information Description
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180 EGA/VGA 16 Color Palette Information
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182 In standard RGB format (IBM EGA, IBM VGA) the data is stored as 16 triples.
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183 Each triple is a 3 byte quantity of Red, Green, Blue values. The values can
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184 range from 0-255, so some interpretation may be necessary. On an IBM EGA,
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185 for example, there are 4 possible levels of RGB for each color. Since
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186 256/4 = 64, the following is a list of the settings and levels:
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194 VGA 256 Color Palette Information
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196 ZSoft has recently added the capability to store palettes containing more
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197 than 16 colors in the .PCX image file. The 256 color palette is formatted
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198 and treated the same as the 16 color palette, except that it is substantially
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199 longer. The palette (number of colors x 3 bytes in length) is appended to
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200 the end of the .PCX file, and is preceded by a 12 decimal. Since the VGA
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201 device expects a palette value to be 0-63 instead of 0-255, you need to
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202 divide the values read in the palette by 4.
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204 To access a 256 color palette:
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206 First, check the version number in the header; if it contains a 5 there is
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209 Second, read to the end of the file and count back 769 bytes. The value
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210 you find should be a 12 decimal, showing the presence of a 256 color palette.
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212 \f24-Bit .PCX Files
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214 24 bit images are stored as version 5 or above as 8 bit, 3 plane images.
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216 24 bit images do not contain a palette.
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218 Bit planes are ordered as lines of red, green, blue in that order.
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220 CGA Color Palette Information
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222 NOTE: This is no longer supported for PC Paintbrush IV/IV Plus.
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224 For a standard IBM CGA board, the palette settings are a bit more complex.
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225 Only the first byte of the triple is used. The first triple has a valid
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226 first byte which represents the background color. To find the background,
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227 take the (unsigned) byte value and divide by 16. This will give a result
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228 between 0-15, hence the background color. The second triple has a valid
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229 first byte, which represents the foreground palette. PC Paintbrush supports
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230 8 possible CGA palettes, so when the foreground setting is encoded between
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231 0 and 255, there are 8 ranges of numbers and the divisor is 32.
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237 Background color is determined in the upper four bits.
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241 Only upper 3 bits are used, lower 5 bits are ignored. The first three bits
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242 that are used are ordered C, P, I. These bits are interpreted as follows:
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244 c: color burst enable - 0 = color; 1 = monochrome
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246 p: palette - 0 = yellow; 1 = white
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248 i: intensity - 0 = dim; 1 = bright
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250 \fPC Paintbrush Bitmap Character Format
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252 NOTE: This format is for PC Paintbrush (up to Vers 3.7) and PC Paintbrush
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253 Plus (up to Vers 1.65)
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255 The bitmap character fonts are stored in a particularly simple format. The
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256 format of these characters is as follows:
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261 font width byte 0xA0 + character width (in pixels)
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262 font height byte character height (in pixels)
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264 Character Width Table
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266 char widths (256 bytes) each char's width + 1 pixel of kerning
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270 (remainder of the file) starts at char 0 (Null)
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272 The characters are stored in ASCII order and as many as 256 may be provided.
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273 Each character is left justified in the character block, all characters take
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274 up the same number of bytes.
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276 Bytes are organized as N strings, where each string is one scan line of the
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279 For example, each character in a 5x7 font requires 7 bytes. A 9x14 font
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280 uses 28 bytes per character (stored two bytes per scan line in 14 sets of
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281 2 byte packets). Custom fonts may be any size up to the current maximum of
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282 10K bytes allowed for a font file. There is a maximum of 4 bytes per scan
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285 \fSample "C" Routines
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287 The following is a simple set of C subroutines to read data from a .PCX file.
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289 /* This procedure reads one encoded block from the image file and stores a
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290 count and data byte.
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292 Return result: 0 = valid data stored, EOF = out of data in file */
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294 encget(pbyt, pcnt, fid)
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295 int *pbyt; /* where to place data */
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296 int *pcnt; /* where to place count */
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297 FILE *fid; /* image file handle */
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300 *pcnt = 1; /* assume a "run" length of one */
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301 if (EOF == (i = getc(fid)))
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303 if (0xC0 == (0xC0 & i))
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306 if (EOF == (i = getc(fid)))
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312 /* Here's a program fragment using encget. This reads an entire file and
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313 stores it in a (large) buffer, pointed to by the variable "bufr". "fp" is
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314 the file pointer for the image */
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318 lsize = (long )hdr.BytesPerLine * hdr.Nplanes * (1 + hdr.Ymax - hdr.Ymin);
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319 for (l = 0; l < lsize; ) /* increment by cnt below */
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321 if (EOF == encget(&chr, &cnt, fp))
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323 for (i = 0; i < cnt; i++)
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328 The following is a set of C subroutines to write data to a .PCX file.
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330 /* Subroutine for writing an encoded byte pair (or single byte if it
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331 doesn't encode) to a file. It returns the count of bytes written, 0 if error */
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333 encput(byt, cnt, fid)
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334 unsigned char byt, cnt;
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338 if ((cnt == 1) && (0xC0 != (0xC0 & byt)))
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340 if (EOF == putc((int )byt, fid))
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341 return(0); /* disk write error (probably full) */
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346 if (EOF == putc((int )0xC0 | cnt, fid))
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347 return (0); /* disk write error */
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348 if (EOF == putc((int )byt, fid))
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349 return (0); /* disk write error */
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356 \f/* This subroutine encodes one scanline and writes it to a file.
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357 It returns number of bytes written into outBuff, 0 if failed. */
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359 encLine(inBuff, inLen, fp)
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360 unsigned char *inBuff; /* pointer to scanline data */
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361 int inLen; /* length of raw scanline in bytes */
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362 FILE *fp; /* file to be written to */
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364 unsigned char this, last;
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366 register int total;
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367 register unsigned char runCount; /* max single runlength is 63 */
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372 /* Find the pixel dimensions of the image by calculating
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373 [XSIZE = Xmax - Xmin + 1] and [YSIZE = Ymax - Ymin + 1].
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374 Then calculate how many bytes are in a "run" */
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376 for (srcIndex = 1; srcIndex < inLen; srcIndex++)
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378 this = *(++inBuff);
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379 if (this == last) /* There is a "run" in the data, encode it */
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382 if (runCount == 63)
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384 if (! (i = encput(last, runCount, fp)))
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390 else /* No "run" - this != last */
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394 if (! (i = encput(last, runCount, fp)))
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402 if (runCount) /* finish up */
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404 if (! (i = encput(last, runCount, fp)))
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406 return (total + i);
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411 \fFRIEZE Technical Information
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413 General FRIEZE Information
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415 FRIEZE is a memory-resident utility that allows you to capture and save
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416 graphic images from other programs. You can then bring these images into
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417 PC Paintbrush for editing and enhancement.
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419 FRIEZE 7.10 and later can be removed from memory (this can return you up
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420 to 90K of DOS RAM, depending on your configuration). To remove FRIEZE from
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421 memory, change directories to your paintbrush directory and type the word
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424 7.00 and Later FRIEZE
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426 The FRIEZE command line format is:
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428 FRIEZE {PD} {Xn[aarr]} {flags} {video} {hres} {vres} {vnum}
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430 {PD} Printer driver filename (without the .PDV extension)
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432 X=S for Serial Printer, P for Parallel Printer, D for disk file.
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433 (file is always named FRIEZE.PRN)
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435 aa = Two digit hex code for which return bits cause
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436 an abort (optional)
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437 rr = Two digit hex code for which return bits cause
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439 NOTE: These codes represent return values from serial or
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440 parallel port BIOS calls. For values see and IBM
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441 BIOS reference (such as Ray Duncan's Advanced MS-DOS
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443 {flags}Four digit hex code
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444 First Digit controls Length Flag
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445 Second Digit controls Width Flag
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446 Third Digit controls Mode Flag
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447 Fourth Digit controls BIOS Flag
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449 1 - Dual Monitor Present
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450 2 - Use internal (true) B/W palette for dithering
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452 4 - Capture palette along with screen IN VGA ONLY
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453 Frieze 8.08 & up ONLY)
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455 NOTE: The length, width and mode flags are printer driver specific.
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456 See PRINTERS.DAT on disk 1 (or Setup Disk) for correct use. In general
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457 width flag of 1 means wide carriage, and 0 means standard width. Length
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458 flag of 0 and mode flag of 0 means use default printer driver settings.
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460 If you need to use more than one BIOS flag option, add the needed flag values
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461 and use the sum as the flag value.
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463 {video} Video driver combination, where the leading digit signifies the
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464 high level video driver and the rest signifies the low
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466 Example = 1EGA - uses DRIVE1 and EGA.DEV
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467 {hres} Horizontal resolution of the desired graphics mode
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468 {vres} Vertical resolution of the desired graphics mode
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469 {vnum} Hardware specific parameter (usually number of color planes)
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471 Note: The last four parameters can be obtained from the CARDS.DAT file,
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472 in your PC Paintbrush product directory.
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475 FRIEZE Function Calls
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477 FRIEZE is operated using software interrupt number 10h (the video interrupt
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480 To make a FRIEZE function call, load 75 (decimal) into the AH register and
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481 the function number into the CL register, then either load AL with the
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482 function argument or load ES and BX with a segment and offset which point
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483 to the function argument. Do an int 10h. FRIEZE will return a result code
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484 number in AX. All other registers are preserved. In general, a result
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485 code of 0 means success and other values indicate errors. However, function
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486 20 (get Frieze Version) behaves differently; see below.
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487 No. Definition Arguments
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490 ES:BX - string (filename to read from)
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492 ES:BX - string (filename to write to)
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497 ES:BX - 4 element word vector of window settings:
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498 Xmin, Ymin, Xmax, Ymax
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501 ES:BX - 16 element vector of byte values
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502 containing the screen-to-printer color correspondence
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504 ES:BX - room for 16 bytes as above
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508 ES:BX - room for 4 words of the current window
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510 16 Set Print Options
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511 ES:BX - character string of printer options.
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512 Same format as for the FRIEZE command.
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513 17, 18, 19 Reserved
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514 20 Get FRIEZE Version.
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515 AH gets the whole number portion and AL gets the
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516 decimal portion of the version number. (eg. for
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517 Freize vesion 7.41, AH will contain 7 and AL will
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518 contain 41. If AH =0, you are calling a pre-7.0
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519 version of FRIEZE).
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521 ES:BX points to an 8 word table (16 bytes) of
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522 parameter settings: TopMargin, LeftMargin,
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523 HSize,VSize, Quality/Draft Mode, PrintHres,
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524 PrintVres, Reserved.
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525 Margins and sizes are specified in hundredths
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527 Q/D mode parameter values:
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528 0 - draft print mode
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529 1 - quality print mode
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530 Print resolutions are specified in DPI.
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531 Any parameter which should be left unchanged may
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532 be filled with a (-1) (0FFFF hex). The reserved
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533 settings should be filled with a (-1).
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535 ES:BX points to an 8 word table (16 bytes) where
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536 parameter settings are held.
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538 ES:BX points to a 12 word table (24 bytes) that
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539 holds six printer resolution pairs.
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540 24 Reserved (versions 8.00 & up)
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544 When FRIEZE is called using interrupt 10 hex, it will return an error code
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545 in the AX register. A value of zero shows that there was no error. A
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546 nonzero result means there was an error. These error codes are explained
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550 1 Printout was stopped by user with the ESC key
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555 6 Invalid Header - not an image, wrong screen mode
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557 8 Disk error - usually drive door open
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558 9 Printer error - printer is off or out of paper
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559 10 Invalid command - CL was set to call a nonexistent FRIEZE function
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560 11 Can't create file - write protect tab or disk is full
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561 12 Wrong video mode - FRIEZE cannot capture text screens.
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563 Technical Reference Manual
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565 Including information for:
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566 Publisher's Paintbrushr
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568 PC Paintbrush IV PlusTM
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569 PC Paintbrush PlusTM
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576 450 Franklin Rd. Suite 100
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582 Copyright c 1985, 1987, 1988, 1990, 1991, ZSoft Corporation
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583 All Rights Reserved
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projects / 16.git / blob