ref: 2b5db0d9d451dafa70039dc0a668cde68e59d4f3
dir: /sys/lib/ghostscript/gs_img.ps/
% (C) 2002 Artifex, Inc. All rights reserved.
%
% This software is provided AS-IS with no warranty, either express or
% implied.
%
% This software is distributed under license and may not be copied,
% modified or distributed except as expressly authorized under the terms
% of the license contained in the file LICENSE in this distribution.
%
% For more information about licensing, please refer to
% http://www.ghostscript.com/licensing/. For information on
% commercial licensing, go to http://www.artifex.com/licensing/ or
% contact Artifex Software, Inc., 101 Lucas Valley Road #110,
% San Rafael, CA 94903, U.S.A., +1(415)492-9861.
% $Id: gs_img.ps,v 1.3 2002/10/08 00:49:48 dan Exp $
% image, colorimage, and imagemask implementation
%
% The design of the overprint facility in Ghostscript requires that color
% specifications include the color space from which they were expressed,
% even after conversion to the device color model. Directly including this
% information in color specifications is usually not efficient, and is
% difficult to integrate into the existing code structure. The alternative
% approach taken is to extend a state mechanism through the device
% interface, and make the current color space, or more specifically,
% certain information about the current color space, a property of this
% state.
%
% For such a mechanism to work, it is necessary to identify all changes
% to the current color space. This is accomplished in the graphic library
% by funneling all changes to the current color space through the
% gs_setcolorspace procedure. At the PostScript interpreter level, this
% result is achieved by forcing color space changes through the
% setcolorspace operator.
%
% Aside from explicit use of setcolorspace, PostScript provides a few
% implicit methods of changing the current color space. The setgray,
% setrgbcolor, and setcmykcolor operators implicitly set the color space
% while explicitly setting the current color. Similarly, the colorimage
% operator and the traditional form of the image operator (5 operands)
% both temporarily modify the current color space while an image is
% being processed. The current file is concerned with the implementation
% of these two operators. In addition, the traditional form of the
% imagemask operator (5 operands), while it does not affect the current
% color space, is closely related to the image operator and thus is
% implemented in this file as well.
%
% In this implementation, all sampled objects are passed through one of
% the internal operators .image1, .imagemask1, .image1alpha, .image2,
% .image3, or .image4, each of which handles a specific ImageType value.
%
% The procedures in this file are responsible for constructing
% image dictionaries from a set of stack entries. This is, in principle,
% a trivial exercise. In practice it appears to be far more complex,
% primarily due to the need to reconstruct the original state in the
% event of an error. This is a particular problem for operators such as
% image, which include data source objects that may, directly or
% indirectly, be procedures. When these procedures are executed, the
% image operator's operands must have been cleared from the operand
% stack. Hence, the operand stack cannot be used to store state
% information. Similarly, the dictionary stack also cannot be used to
% store state information, as the data source procedures may depend on
% a particular dictionary being on the top of this stack.
%
% Adobe's PostScript implementations determine the extent to which the
% interpreter state is restored in the event of an error by the point at
% which the error is detected. Errors in the image/colorimage/imagemask
% operators that are detected before the data source procedures are
% executed restore the state in effect before the image was processed.
% Those that are detected as part of running the data source procedures
% only attempt to restore the state to that in effect at the start of
% the operator that failed (or at the conclusion of the data source
% procedure, if this procedure failed to push a string).
%
% The implementation given here follows the Adobe convention. The
% mechanism used is as follows:
%
% 1. Check that the stack has a sufficient number of operands, and
% that enough of them have the proper type to allow construction
% of the image dictionary. Any errors at this point are handled
% in the conventional manner.
%
% 2. Build the image dictionary, in the process clearing the image/
% colorimage/imagemask operands from the stack. No errors can
% occur during this process.
%
% (Special precautions could be taken during this step to handle
% a limitcheck or VMError during the building of the image
% dictionary, but this essentially never occurs in practice and, if
% it did, is very unlikely to leave a useable state. Hence, we don't
% bother with this possibility.)
%
% 3. The .image operator is executed in a stopped context. If it
% returns abnormally, a check is made to see if the uppermost
% operand on the stack is a color image dictionary. If so, the
% original stack is created anew using this dictionary. (Because
% the image operand works via colorimage, some additional special
% handling is required in this case.)
%
%
% Create a dictionary of operators for specific image and image mask types.
% Each of these will always handle ImageType 1. Additional types are added
% as they are supported in specific interpreter levels or versions.
%
% These dictionaries are in systemdict for historical reasons.
%
.currentglobal true .setglobal
systemdict begin
/.imagetypes
5 dict
dup 1 /.image1 load put
def
/.imagemasktypes
5 dict
dup 1 /.imagemask1 load put
def
end
.setglobal
%
% Build a dictionary of utility procedures and constants for use in
% impelementing the image operators. This dictionary is in global VM but
% is maintained (during initialization) in userdict. It should be pushed
% onto the dictionary stack when constructing image-related procedures
% and pseudo-operators.
%
% This dictionary is removed from userdict when initialization is
% completed.
%
.currentglobal true .setglobal
userdict /img_utils_dict 30 dict put
img_utils_dict begin
%
% Some useful local data structures:
%
% img_csary maps the number of components in an image to the implied
% color space.
%
% img_decary is a prototype Decode array; subintervals of this array
% may be used for fewer than 4 color components.
%
% img_params_ary is a list of the parameters to be built in the image
% dictionary for a colorimage invocation. ImageType is given a
% fixed value; the other parameters are in stack order (IMG_NComps
% is the number of components).
%
% img_mask_params_ary is the equivalent of img_params_ary for imagemask
% invocations. Polarity is a proxy for Decode, and is replaced
% by the Decode key in the image dictionary.
%
% img_mask_check_ary is the set of parameters that must be present in
% an image dictionary generated by an imagemask invocation. This
% differs from img_mask_params_ary in that Decode replaces Polarity.
%
/img_csary [ null /DeviceGray null /DeviceRGB /DeviceCMYK ] def
/img_decary [ 0 1 0 1 0 1 0 1 ] def
/img_params_ary
[
/ImageType /IMG_NComps /MultipleDataSources /DataSource
/ImageMatrix /BitsPerComponent /Height /Width /Decode
]
def
/img_check_ary //img_params_ary def
/img_unbuild_ary
//img_params_ary 1 1 index length 2 sub getinterval
def
/img_mask_params_ary
[ /ImageType /DataSource /ImageMatrix /Polarity /Height /Width ]
def
/img_mask_check_ary
[
/ImageType /BitsPerComponent
/DataSource /ImageMatrix /Decode /Height /Width
]
def
/img_mask_unbuild_ary
//img_mask_check_ary 2 1 index length 2 sub getinterval
def
%
% <?any?> <array> img_check_keys <?any?> <bool>
%
% Verify that:
% that there are at least two entries on the stack, and
% the second (lower) entry is a dictionary, and
% that dictionary contains all of the keys in the array
%
% If any one of these conditions does not hold, pop the array and push
% false; otherwise pop the array and push true. This utility is used by
% the colorimage and imagematrix procedures to determine if .image left
% the image dictionary on the stack after an abnormal return.
%
/img_check_keys
{
count 2 ge
{
1 index type /dicttype eq
{
true exch
{
2 index exch known and
dup not
{ exit }
if
}
forall
}
{ pop //false }
ifelse
}
{ pop //false }
ifelse
}
.bind def
%
% Procedures to convert a set of stack entries to a dictionary. There is
% a procedure associated with each key, though most keys use the same
% procedure. The dictionary to be built is at the top of the dictionary
% stack. Stack handling for the procedures is:
%
% <?val0?> ... <?val(n - 1)?> <key> proc -
%
% Parameters are handle in inverse-stack order, so inter-parameter
% dependencies that on the stack can generally be used here.
%
/img_params_dict
mark
/ImageType { 1 def } .bind
/IMG_NComps { exch def } .bind % number of components
/MultipleDataSources 1 index
/Width 1 index
/Height 1 index
/ImageMatrix 1 index
/BitsPerComponent 1 index
/DataSource 1 index
% Polarity is a proxy for Decode; it never appears in a dictionary
/Polarity
{
pop
{ { 1 0 } }
{ { 0 1 } }
ifelse
/Decode exch cvlit def
}
.bind
% the definition of Decode is based on the number of components
/Decode { //img_decary 0 IMG_NComps 2 mul getinterval def } .bind
.dicttomark
def
%
% <oper_0> ... <oper_n> <array> img_build_dict <dict>
%
% Build a dictionary. This will always be done in local VM. The array is
% a list of the keys to be associated with operands on the stack, in
% inverse stack order (topmost element first). The caller should verify
% that the dictionary can be built successfully (except for a possible
% VMerror) before calling this routine.
%
/img_build_dict
{
% build the dictionary in local VM; all for 2 extra entries
.currentglobal false .setglobal
1 index length 2 add dict
exch .setglobal
begin
% process all keys in the array
{ //img_params_dict 1 index get exec }
forall
% if BitsPerComponent is not yet defined, define it to be 1
currentdict /BitsPerComponent known not
{ /BitsPerComponent 1 def }
if
currentdict end
}
.bind def
%
% <dict> <array> img_unbuild_dict <oper_0> ... <oper_n>
%
% "Unbuild" a dictionary: spread the contents the dictionary back onto the
% stack, in the inverse of the order indicated in the array (inverse is
% used as this order is more convenient for img_build_dict, which is
% expected to be invoked far more frequently).
%
/img_unbuild_dict
{
exch begin
dup length 1 sub -1 0
{ 1 index exch get load exch }
for
pop
end
}
.bind def
%
% <width> <height> <bits/component> <matrix> <dsrc0> ...
% <multi> <ncomp> <has_alpha>
% img_build_image_dict
% <dict> <has_alpha>
%
% Build the dictionary corresponding to a colorimage operand stack. This
% routine will check just enough of the stack to verify that the
% dictionary can be built, and will generate the appropriate error if this
% is not the case.
%
% The <has_alpha> boolean is used to support the Next alphaimage extension.
%
% At the first level, errors in this procedure are reported as colorimage
% errors. The error actually reported will usually be determined by the
% pseudo-operator which invokes this routine.
%
/img_build_image_dict
{
% Veify that at least 8 operands are available, and that the top three
% operands have the expected types
count 8 lt
{ /.colorimage cvx /stackunderflow signalerror }
if
3 copy
type /booleantype ne exch
type /integertype ne or exch
type /booleantype ne or
{ /.colorimage cvx /typecheck signalerror }
if
% verify that the number of components is 1, 3, or 4
1 index 1 lt 2 index 2 eq or 2 index 4 gt or
{ /.colorimage cvx /rangecheck signalerror }
if
% Verify that the required number of operands are present if multiple
% data sources are being used. If this test is successful, convert
% the data sources to an array (in local VM).
2 index
{
% if an alpha component is present, this adds one more component
2 copy
{ 1 add }
if
dup count 9 sub gt
{ /.colorimage cvx /stackunderflow signalerror }
if
% build the DataSource array in local VM
dup .currentglobal false .setglobal exch array exch .setglobal
% stack: <w> <h> <bps> <mtx> <d0> ... <multi> <n> <alpha> <n'> <array>
5 1 roll 4 add 3 roll astore 4 1 roll
}
if
% the image dictionary can be built; do so
% stack: <w> <h> <bps> <mtx> <dsrc|dsrc_array> <multi> <n> <alpha>
8 1 roll //img_params_ary //img_build_dict exec exch
}
.bind def
%
% <?dict?>
% img_unbuild_image_dict
% <width> <height> <bits/component> <matrix> <dsrc0> ...
% <multi> <ncomp>
%
% If the top entry of the stack is a dictionary that has the keys required
% by a colorimage dictionary, unpack that dictionary onto the stack.
% Otherwise just leave things as they are. Note that the <has_alpha>
% parameter is not pushd onto the stack.
%
/img_unbuild_image_dict
{
//img_check_ary //img_check_keys exec
{
//img_unbuild_ary //img_unbuild_dict exec
1 index type /booleantype eq
{
1 index
{ 3 1 roll aload length 2 add -2 roll }
if
}
if
}
if
}
.bind def
%
% <width> <height> <polarity> <matrix> <dsrc>
% img_unbuild_imagemask_dict
% <dict>
%
% Build the dictionary corresponding to an imagemask stack. This routine
% will verify that the appropriate number of operands are on the stack,
% and that polarity is a boolean. This is all that is necessary to build
% the dictionary.
%
/img_build_imagemask_dict
{
% check for proper number of operands
count 5 lt
{ /imagemask load /stackunderflow signalerror }
if
% verify that polarity is a boolean
2 index type /booleantype ne
{ /imagemask load /typecheck signalerror }
if
% the imagemask dictionary can be built; do so
//img_mask_params_ary //img_build_dict exec
}
.bind def
%
% <?dict?>
% img_unbuild_imagemask_dict
% <width> <height> <polarity> <matrix> <dsrc>
%
% If the top entry of the stack is a dictionary that has the keys rquired
% by an imagemask dictionary, unpack that dictionary onto the stack.
% Otherwise just leave things as they are.
%
/img_unbuild_imagemask_dict
{
//img_mask_check_ary //img_check_keys exec
{
//img_mask_unbuild_ary //img_unbuild_dict exec
3 -1 roll
dup type dup /arraytype eq exch /packedarraytype eq or
1 index rcheck and
{ 0 get 1 eq }
if
3 1 roll
}
if
}
.bind def
%
% <width> <height> <bits/component> <matrix> <dsrc_0> ...
% <multi> <ncomp> <has_alpha>
% .colorimage
% -
%
% Convert the image/colorimage operator from their traditional form to
% the dictionary form. The <has_alpha> operand is used ot support the
% Next alphaimage extension.
%
% Error handling for these operators is a bit complex, due to the stack
% handling required of operators that potentially invoke procedures.
% This problem is discussed in the comment above. The facts relevant to
% this particular implementation are:
%
% 1. The .image1 (or .alphaimage) operator is executed in a stopped
% context, so that we can undo the gsave context in the event of
% an error.
%
% 2. In the event of an error, the stack is examined to see if the
% dictionary passed to .image1 (.alphaimage) is still present.
% If so, this dictionary is "unpacked" onto the stack to re-
% create the original stack. The <has_alpha> parameter is not
% pushed onto the stack, as it is not required for any of the
% pseudo-operators than invoke this procedure.
%
% 3. The use of pseudo-operators in this case may yield incorrect
% results for late-detected errors, as the stack depth will be
% restored (even though the stack is not). This is, however, no
% worse than the prior (level >= 2) code, so it should cause no
% new problems.
%
/.colorimage
{
% build the image dictionary
//img_build_image_dict exec
% execute .image1 in a stopped context
{
gsave
0 .setoverprintmode % disable overprint mode for images
//img_csary 2 index /IMG_NComps get get setcolorspace
{ .alphaimage }
{ .image1 }
ifelse
}
stopped
grestore
{
//img_unbuild_image_dict exec
/.colorimage cvx $error /errorname get
signalerror
}
if
}
.bind def
%
% <width> <height> <bits/component> <matrix> <dsrc_0> ...
% <multi> <ncomp>
% colorimage
% -
%
% Build the colorimage pseudo-operator only if setcolorscreen is visible.
%
systemdict /setcolorscreen .knownget
{
type /operatortype eq
{
/colorimage
{
//false
//.colorimage
stopped
{ /colorimage load $error /errorname get signalerror }
if
}
.bind systemdict begin odef end
}
if
}
if
%
% width height bits_per_component matrix data_src image -
%
% <dict> image -
%
% Some special handling is required for ImageType 2 (Display PostScript
% pixmap images) so as to set the appropriate color space as the current
% color space.
%
/image
{
dup type /dicttype eq languagelevel 2 ge and
{
dup /ImageType get dup 2 eq
{
% verify the ImageType 2 is supported
//.imagetypes exch known
{
%
% Set either DevicePixel or DeviceRGB as the current
% color space. DevicePixel is used if the image data is
% to be copied directly, with only a geometric
% transformation (PixelCopy true). The use of DeviceRGB
% in the alternate case is not, in general, correct, and
% reflects a current implementation limitation. Ideally,
% an intermediate color space should be used only if
% the source and destination color models vary; otherwise
% the native color space corresponding to the color model
% should be used.
%
% The mechanism to determine depth for the DevicePixel
% color space when BitsPerPixel is not available is
% somewhat of a hack.
%
gsave
0 .setoverprintmode % disable overprintmode for images
dup /PixelCopy .knownget dup
{ pop }
if
{
[
/DevicePixel
currentpagedevice dup /BitsPerPixel .knownget
{ exch pop }
{
/GrayValues .knownget not
{ 2 } % try a guess
if
ln 2 ln div round cvi
}
ifelse
]
}
{ /DeviceRGB }
ifelse
setcolorspace
//.imagetypes 2 get
stopped
grestore
{ /image load $error /errorname get signalerror }
if
}
{ /image load /undefined signalerror }
ifelse
}
{
gsave
0 .setoverprintmode % disable overprintmode for images
//.imagetypes exch get
stopped
grestore
{ /image load $error /errorname get signalerror }
if
}
ifelse
}
{
//false 1 //false
//.colorimage
stopped
{ /image load $error /errorname get signalerror }
if
}
ifelse
}
.bind systemdict begin odef end
%
% width height polarity matrix datasrc imagemask -
%
% See the comment preceding the definition of .colorimage for information
% as to the handling of error conditions.
%
/imagemask
{
dup type /dicttype eq languagelevel 2 ge and
{ dup /ImageType get //.imagemasktypes exch get exec }
{
//img_build_imagemask_dict exec
{ .imagemask1 }
stopped
{
//img_unbuild_imagemask_dict exec
/imagemask load $error /errorname get signalerror
}
if
}
ifelse
}
.bind systemdict begin odef end
end % img_utils_dict
.setglobal % restore VM mode