gs_img.ps
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% Copyright (C) 2002-2018 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., 1305 Grant Avenue - Suite 200, Novato, % CA 94945, U.S.A., +1(415)492-9861. % 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, .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 % % 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 % % Check the image types that can be used as data sources % <any> foo <bool> % /good_image_types mark /filetype { pop //true } .bind /stringtype 1 index /arraytype //xcheck /packedarraytype //xcheck .dicttomark readonly def % % <width> <height> <bits/component> <matrix> <dsrc0> ... % <multi> <ncomp> % img_build_image_dict % <dict> % % 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. % % 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 { % Verify that at least 7 operands are available, and that the top two % operands have the expected types count 7 lt { /.colorimage cvx /stackunderflow signalerror } if 2 copy type /integertype ne exch type /booleantype ne or { /.colorimage cvx /typecheck signalerror } if % verify that the number of components is 1, 3, or 4 dup 1 lt 1 index 2 eq or 1 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). 1 index { dup dup count 8 sub gt { % Adobe interpreters appear to test the arguments sequentially % starting from the top of the stack and report the 1st error found. % To satisfy CET test 12-02.PS we emulate this logic. //true exch -1 1 { 2 add index //good_image_types 1 index type .knownget { exec and } { pop pop //false } ifelse } for { /stackunderflow } { /typecheck } ifelse /.colorimage cvx exch 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> <n'> <array> 4 1 roll 3 add 2 roll astore 3 1 roll } if % the image dictionary can be built; do so % stack: <w> <h> <bps> <mtx> <dsrc|dsrc_array> <multi> <n> //img_params_ary //img_build_dict exec } .bind def currentdict /good_image_types .undef % % <?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. % /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 .systemvar /stackunderflow signalerror } if % verify that polarity is a boolean 2 index type /booleantype ne { /imagemask .systemvar /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> % .colorimage % - % % Convert the image/colorimage operator from their traditional form to % the dictionary form. % % 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 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 is still present. % If so, this dictionary is "unpacked" onto the stack to re- % create the original stack. % % 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 % The CET test file 12-02.ps creates colorimages with a width and % height of 0. Ignore these since that is what the CET expects. dup dup /Height get 0 eq exch /Width get 0 eq or { pop } % Ignore colorimage. Pop dict { 0 .setoverprintmode % disable overprint mode for images //img_csary 1 index /IMG_NComps get get setcolorspace .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 { //.colorimage stopped { /colorimage .systemvar $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 .systemvar $error /errorname get signalerror } if } { /image .systemvar /rangecheck signalerror } ifelse } { dup //.imagetypes exch .knownget { exch pop gsave 0 .setoverprintmode % disable overprintmode for images stopped grestore { /image .systemvar $error /errorname get signalerror } if } { /image .systemvar exch type /integertype eq { /rangecheck } { /typecheck } ifelse signalerror } ifelse } ifelse } { //false 1 //.colorimage stopped { /image .systemvar $error /errorname get signalerror } if } ifelse } .bind odef % An auxiliary function for checking whether an imagemask to be interpolated. /.is_low_resolution % <image dict> .is_low_resolution <bool> { % Checking whether image pixel maps to more than 2 device pixels. % The threshold 2 is arbitrary. 1 exch 0 exch 0 exch 1 exch /ImageMatrix get dup 2 { 4 1 roll idtransform dtransform dup mul exch dup mul add sqrt } repeat .max 2 gt % arbitrary } .bind def % % 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 .knownget { 1 index //.is_low_resolution exec 2 index /ImageType get 1 eq and 2 index /BitsPerComponent get 1 eq and 2 index /Interpolate .knownget not { //false } if and //filterdict /ImscaleDecode known and %% %% Don't apply ImScaleDecode to interpolate imagemasks if %% the current device is a high level device. %% /HighLevelDevice /GetDeviceParam .special_op { exch pop not }{ //true }ifelse and { % Apply interpolated imagemask scaling filter exch .currentglobal exch dup .gcheck .setglobal dup length dict .copydict dup dup /DataSource get dup type /stringtype eq { 1 array astore cvx % image.* operators read strings repeatesly } if mark /Width 3 index /Width get /Height 5 index /Height get .dicttomark /ImscaleDecode filter /DataSource exch put dup dup /Width get 4 mul /Width exch put dup dup /Height get 4 mul /Height exch put dup dup /ImageMatrix get { 4 0 0 4 0 0 } matrix concatmatrix /ImageMatrix exch put 3 1 roll .setglobal } if exec } { % CET 12-08b.ps wants /typecheck /imagemask .systemvar /typecheck signalerror } ifelse } { //img_build_imagemask_dict exec { .imagemask1 } stopped { //img_unbuild_imagemask_dict exec /imagemask .systemvar $error /errorname get signalerror } if } ifelse } .bind odef % undefine a bunch of local definitions [ /.colorimage /img_params_dict /img_unbuild_dict /img_unbuild_image_dict /img_unbuild_imagemask_dict /img_build_dict /img_build_image_dict /img_build_imagemask_dict /img_check_keys /img_mask_check_ary /img_params_ary /img_mask_unbuild_ary /img_mask_params_ary /img_csary /img_decary /img_check_ary /img_unbuild_ary /.is_low_resolution ] {currentdict exch .undef} forall end % systemdict .setglobal % restore VM mode
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