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diff --git a/man/man7/image.html b/man/man7/image.html deleted file mode 100644 index f81c023b..00000000 --- a/man/man7/image.html +++ /dev/null @@ -1,175 +0,0 @@ -<head> -<title>image(7) - Plan 9 from User Space</title> -<meta content="text/html; charset=utf-8" http-equiv=Content-Type> -</head> -<body bgcolor=#ffffff> -<table border=0 cellpadding=0 cellspacing=0 width=100%> -<tr height=10><td> -<tr><td width=20><td> -<tr><td width=20><td><b>IMAGE(7)</b><td align=right><b>IMAGE(7)</b> -<tr><td width=20><td colspan=2> - <br> -<p><font size=+1><b>NAME </b></font><br> - -<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> - - image – external format for images<br> - -</table> -<p><font size=+1><b>SYNOPSIS </b></font><br> - -<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> - - <tt><font size=+1>#include <draw.h><br> - </font></tt> -</table> -<p><font size=+1><b>DESCRIPTION </b></font><br> - -<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> - - Images are described in <a href="../man3/graphics.html"><i>graphics</i>(3)</a>, and the definition of pixel - values is in <a href="../man7/color.html"><i>color</i>(7)</a>. Fonts and images are stored in external - files in machine-independent formats. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - Image files are read and written using <tt><font size=+1>readimage</font></tt> and <tt><font size=+1>writeimage</font></tt> - (see <a href="../man3/allocimage.html"><i>allocimage</i>(3)</a>),<i>or</i> <tt><font size=+1>readmemimage</font></tt> and <tt><font size=+1>writememimage</font></tt> (see <a href="../man3/memdraw.html"><i>memdraw</i>(3)</a>). - An uncompressed image file starts with 5 strings: <tt><font size=+1>chan</font></tt>, <tt><font size=+1>r.min.x</font></tt>, - <tt><font size=+1>r.min.y</font></tt>, <tt><font size=+1>r.max.x</font></tt>, and <tt><font size=+1>r.max.y</font></tt>. Each is right-justified and blank - padded in 11 - characters, followed by a blank. The <tt><font size=+1>chan</font></tt> value is a textual string - describing the pixel format (see <tt><font size=+1>strtochan</font></tt> in <a href="../man3/graphics.html"><i>graphics</i>(3)</a> and - the discussion of channel descriptors below), and the rectangle - coordinates are decimal strings. The rest of the file contains - the <tt><font size=+1>r.max.y−r.min.y</font></tt> rows of pixel data. A <i>row</i> consists - of the byte containing pixel <tt><font size=+1>r.min.x</font></tt> and all the bytes up to and - including the byte containing pixel <tt><font size=+1>r.max.x</font></tt>-1. For images with - depth <i>d</i> less than eight, a pixel with x-coordinate = <i>x</i> will appear - as <i>d</i> contiguous bits in a byte, with the pixel’s high order bit - starting at the byte’s bit number <i>w</i>×(<i>x</i> mod (8/<i>w</i>)), where - bits within a byte are numbered 0 to 7 from the high order to - the low order bit. Rows contain integral number of bytes, so there - may be some unused pixels at either end of a row. If <i>d</i> is greater - than 8, the definition of images requires that it will a multiple - of 8, so pixel values take up an integral number of bytes. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - The <tt><font size=+1>loadimage</font></tt> and <tt><font size=+1>unloadimage</font></tt> functions described in <a href="../man3/allocimage.html"><i>allocimage</i>(3)</a> - also deal with rows in this format, stored in user memory. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - The channel format string is a sequence of two-character channel - descriptions, each comprising a letter (<tt><font size=+1>r</font></tt> for red, <tt><font size=+1>g</font></tt> for green, - <tt><font size=+1>b</font></tt> for blue, <tt><font size=+1>a</font></tt> for alpha, <tt><font size=+1>m</font></tt> for color-mapped, <tt><font size=+1>k</font></tt> for greyscale, - and <tt><font size=+1>x</font></tt> for “don’t care”) followed by a number of bits per pixel. - The sum of the channel bits per pixel is the depth of the image, - which must be either a divisor or a multiple of eight. It is an - error to have more than one of any channel but <tt><font size=+1>x</font></tt>. An image must - have either a greyscale channel; a color mapped channel; or red, - green, and blue channels. If the alpha channel is present, it - must be at least as deep as any other channel. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - The channel string defines the format of the pixels in the file, - and should not be confused with ordering of bytes in the file. - In particular <tt><font size=+1>'r8g8b8'</font></tt> pixels have byte ordering blue, green, - and red within the file. See <a href="../man7/color.html"><i>color</i>(7)</a> for more details of the - pixel format. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - A venerable yet deprecated format replaces the channel string - with a decimal <i>ldepth</i>, which is the base two logarithm of the - number of bits per pixel in the image. In this case, <i>ldepth</i>s 0, - 1, 2, and 3 correspond to channel descriptors <tt><font size=+1>k1</font></tt>, <tt><font size=+1>k2</font></tt>, <tt><font size=+1>k4</font></tt>, and - <tt><font size=+1>m8</font></tt>, respectively. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - Compressed image files start with a line of text containing the - word <tt><font size=+1>compressed</font></tt>, followed by a header as described above, followed - by the image data. The data, when uncompressed, is laid out in - the usual form. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - The data is represented by a string of compression blocks, each - encoding a number of rows of the image’s pixel data. Compression - blocks are at most 6024 bytes long, so that they fit comfortably - in a single 9P message. Since a compression block must encode - a whole number of rows, there is a limit (about 5825 - bytes) to the width of images that may be encoded. Most wide images - are in subfonts, which, at 1 bit per pixel (the usual case for - fonts), can be 46600 pixels wide. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - A compression block begins with two decimal strings of twelve - bytes each. The first number is one more than the <tt><font size=+1>y</font></tt> coordinate - of the last row in the block. The second is the number of bytes - of compressed data in the block, not including the two decimal - strings. This number must not be larger than 6000. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - Pixels are encoded using a version of Lempel & Ziv’s sliding window - scheme LZ77, best described in J A Storer & T G Szymanski ‘Data - Compression via Textual Substitution’, JACM 29#4, pp. 928-951. - - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - The compression block is a string of variable-length code words - encoding substrings of the pixel data. A code word either gives - the substring directly or indicates that it is a copy of data - occurring previously in the pixel stream. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - In a code word whose first byte has the high-order bit set, the - rest of the byte indicates the length of a substring encoded directly. - Values from 0 to 127 encode lengths from 1 to 128 bytes. Subsequent - bytes are the literal pixel data. - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - If the high-order bit is zero, the next 5 bits encode the length - of a substring copied from previous pixels. Values from 0 to 31 - encode lengths from 3 to 34 bytes. The bottom two bits of the - first byte and the 8 bits of the next byte encode an offset backward - from the current position in the pixel data at which the copy - is to be found. Values from 0 to 1023 encode offsets from 1 to - 1024. The encoding may be ‘prescient’, with the length larger - than the offset, which works just fine: the new data is identical - to the data at the given offset, even though the two strings overlap. - - <table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table> - - Some small images, in particular 48×48 face files as used by <i>seemail</i> - (see Plan 9’s <i>faces</i>(1) and <a href="../man7/face.html"><i>face</i>(7)</a>) and 16×16 cursors, can be stored - textually, suitable for inclusion in C source. Each line of text - represents one scan line as a comma-separated sequence of hexadecimal - bytes, shorts, or words in C format. For - cursors, each line defines a pair of bytes. (It takes two images - to define a cursor; each must be stored separately to be processed - by programs such as <a href="../man1/tweak.html"><i>tweak</i>(1)</a>.) Face files of one bit per pixel - are stored as a sequence of shorts, those of larger pixel sizes - as a sequence of longs. Software that reads these files must - deduce the image size from the input; there is no header. These - formats reflect history rather than design.<br> - -</table> -<p><font size=+1><b>SEE ALSO </b></font><br> - -<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td> - - <a href="../man1/jpg.html"><i>jpg</i>(1)</a>, <a href="../man1/tweak.html"><i>tweak</i>(1)</a>, <a href="../man3/graphics.html"><i>graphics</i>(3)</a>, <a href="../man3/draw.html"><i>draw</i>(3)</a>, <a href="../man3/allocimage.html"><i>allocimage</i>(3)</a>, <a href="../man7/color.html"><i>color</i>(7)</a>, - <a href="../man7/face.html"><i>face</i>(7)</a>, <a href="../man7/font.html"><i>font</i>(7)</a><br> - -</table> - -<td width=20> -<tr height=20><td> -</table> -<!-- TRAILER --> -<table border=0 cellpadding=0 cellspacing=0 width=100%> -<tr height=15><td width=10><td><td width=10> -<tr><td><td> -<center> -<a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a> -</center> -</table> -<!-- TRAILER --> -</body></html> |