.ai export: the pieces of a warped image write only the pixels they show

The pieces of a Warp effect, an envelope or their expanded art each
held a copy of the whole image in the .ai editing data and in legacy
.ai files: 200 copies for a Warp's 10 x 10 mesh.

- An embedded image cut to a clipping path (in the editing data, also
  an image under an opacity mask that clips) is written whole the
  first time; later copies of the same pixels are written as the
  rectangle the path or mask shows, 2 pixels more on each side, with
  the matrix moved to keep their place. A copy that the path shows
  none of is written as one pixel.
- An opacity mask's window covers everything the mask's art paints,
  its effects and symbol art included.
- An image's editable original and an image in an opacity mask's art
  are written whole. A live Warp's drawn look is not cut to the
  clipping groups around the object, so a clipped image with a live
  Warp reads back with its Warp live.
- When art that held an image's whole copy is left out (an opacity
  mask's art, a live envelope or a definition past the object limit),
  the next copy is written whole again. A whole copy written on hidden
  lines after an earlier one leaves the earlier one as the copy that
  counts.
- The writers read an image's pixels once for the pieces that follow
  one another.

Docs: docs/target-app-parity.md.

docs/target-app-parity.md

@@ -616,6 +616,7 @@ since 2026-10-01.
 - **Warp effects bend images:** a Warp effect on an image, or on a group that holds one, bends the image's pixels with its frame, as the Warp effect is documented to distort bitmap images in [Reshaping with effects](https://helpx.adobe.com/illustrator/using/reshaping-objects-effects.html): after the last effect, the image is cut into 10 × 10 cells of two triangles, each a clipped piece under its own affine map. Effects after the Warp reshape only the frame, a second Warp bends the same pieces, and warps saved without a version bend the pixels with their earlier map, as they bend the frame. A placed gradient on a group that holds the image follows the group's bounds as the pieces draw them. SVG writes the image once for the pieces; PDF, EPS, `.ai` and PNG write the bent pieces. The images stay unbent when their pieces would make the art pass 2 million objects, and so does an image whose frame keeps its shape past the anchor budget. A grayscale image's fill color now colorizes the pieces of a warp or an envelope, and an image under any geometry effect keeps that color and its smoothing setting. Existing documents with a Warp effect on an image, or on a group that holds one, draw differently: before, the image showed unbent, cut by the bent frame. So do existing documents with a colorized image under an envelope or a geometry effect, or an image drawn without smoothing under a geometry effect: before, those lost the color or the setting. The cell count and the limits are VectorCraft's own (effects `tests::warped_images_stay_within_the_object_budget`, `tests::warped_images_keep_document_keys_and_hidden_images_apart`, `tests::an_image_whose_frame_passes_the_budget_stays_whole`, `tests::effects_after_a_warp_reshape_an_images_frame_and_not_its_pieces`, `tests::an_images_pixels_take_the_map_their_warps_version_names`, `tests::an_image_under_a_geometry_effect_keeps_its_color_and_smoothing`, `tests::a_nested_groups_gradient_follows_its_warped_image`; engine `warp_images::an_images_pixels_bend_with_effect_warp`, `a_warped_image_keeps_its_bend_in_svg`, `a_warped_image_keeps_its_bend_in_pdf`, `a_warped_image_keeps_its_bend_in_ai`, `a_warped_image_keeps_its_bend_in_eps`, `a_warped_image_keeps_its_bend_in_png`, `svg_writes_an_image_clipped_twice_in_a_users_group_twice`, `expand_appearance_of_a_warped_image_draws_as_the_canvas_did`, `a_colorized_image_keeps_its_color_when_warped`, `a_warp_on_a_group_bends_the_image_in_it`, `envelope_distort::a_colorized_image_keeps_its_color_in_an_envelope`). Scores and hours unchanged.
 - **`.ai` files keep an image's Warp live:** an embedded image whose appearance is one Warp effect, with no opacity mask, is saved to the `.ai` editing data with an art style of that Warp: its bent pieces are its drawn look, and the image itself follows on `%_` lines, as for other styled objects. Opening an `.ai` file reads such an image as the image with its Warp live, its pixels, placement, name and opacity kept, when the live warp draws as the file's drawn look and the import has a comparison left; otherwise the drawn look stays, with the drawn-look note. The Warp effect applies to bitmap images ([the help page](https://helpx.adobe.com/illustrator/desktop/manage-objects/reshape-transform-objects/distort-and-transform-effects-in-illustrator.html)), and native files keep live effects ([the help page](https://helpx.adobe.com/illustrator/desktop/get-started/learn-the-basics/supported-file-formats-in-illustrator.html)). A linked image with a Warp is saved as its drawn art, as before, and its live Warp is not saved. Images with an opacity mask, and images with a Warp and another effect or with another geometry effect, are saved and opened as their drawn art. Existing `.ai` files with an embedded image on `%_` lines open differently: before, that image also came in beside its drawn look. Which images keep the Warp and the comparison are VectorCraft's own rules (eps `ai_editing::tests::an_image_with_a_warp_reads_back_with_its_warp_live`, `an_image_whose_warp_draws_otherwise_than_its_look_keeps_its_look`, `an_image_on_hidden_lines_does_not_come_in_beside_its_look`, `other_warped_images_are_written_as_their_drawn_art`, `import::ai::read::ops::tests::an_image_takes_a_style_of_one_warp_alone`). Scores and hours unchanged.
 - **EPS writes a repeated image's samples once:** an image drawn more than once in an EPS file (the pieces of an envelope or a Warp effect, copies of one image, or one image in a symbol's instances) has its compressed samples written once in the setup, and each placement reads them from there: a reusable stream rewound for each placement at Language Level 3 ([PostScript Language Reference, 3rd ed., §3.13](https://www.adobe.com/jp/print/postscript/pdfs/PLRM.pdf)), and an array of strings of at most 49,152 bytes fed to the image by a procedure at Level 2. An image drawn once is written where it is drawn, as before. The 256 MB limit on the page counts the samples once, so an envelope of a large photo no longer loses pieces to it. A colorized image is reused per ink (eps `tests::an_image_placed_twice_writes_its_samples_once_at_both_levels`, `tests::an_envelopes_image_pieces_draw_one_copy_of_its_samples`, `tests::each_ink_of_a_colorized_image_placed_twice_is_written_once`, `tests::samples_longer_than_a_string_are_reused_at_both_levels`, `tests::the_page_limit_counts_a_repeated_images_samples_once`). Scores and hours unchanged.
+- **`.ai` files write a warped image's pieces as the parts they show:** in the `.ai` editing data and in legacy `.ai` files, an embedded image cut to a clipping path (in the editing data, also an image under an opacity mask that clips) is written with all of its pixels the first time, and every later copy of the same pixels is written as the rectangle of them that the path or mask shows, 2 pixels more on each side, placed where it lies in the image. The pieces of a Warp effect, an envelope or their expanded art, 200 copies of the image for 10 × 10 cells before, now add about twice the image's pixels. Each image's pixels are read once for the pieces that follow one another. An image cut to a rectangle of half its pixels or more, and the first copy written, keep all of their pixels. The `XI` operator's arguments give an image's location and size ([AI file-format specification, §8.1](https://web.archive.org/web/20050126105313/https://partners.adobe.com/public/developer/en/illustrator/sdk/AI7FileFormat.pdf)); the 2-pixel margin and the half-the-pixels limit are VectorCraft's own rules (eps `ai_editing::tests::the_pieces_of_a_warped_image_are_written_as_the_parts_they_show`, `masked_pieces_of_a_warped_image_are_written_as_the_parts_they_show`, `an_image_with_a_live_warp_writes_its_pixels_whole_once`, `a_clipped_image_written_first_keeps_all_of_its_pixels`, `legacy_ai::tests::the_pieces_of_a_warped_image_are_written_as_the_parts_they_show`). Scores and hours unchanged.
 - **Distort Appearance with Transform effect options:** with Envelope Options › Distort Appearance on, a path whose Transform effect has Scale Strokes & Effects or Transform Patterns on, or copies it with a gradient, is bent as the same per-copy art it draws and expands as outside the envelope: each copy's own stroke weight, dashes, pattern placement and gradient (effects `bake::tests`). Scores and hours unchanged.
 - **Fitted gradients turn with the Transform effect:** a gradient fitted to the object (not placed with the Gradient tool) turns, reflects and stretches with the object when its Transform effect rotates, reflects or scales it unevenly, as Object › Transform already does: the gradient is fixed to its fit on the geometry the effect takes, then follows the effect and the effects after it as a placed gradient does. Under moves and even scales it draws as a refit does, and a Transform effect that scales the object to nothing across leaves it fitted, with Scale Strokes & Effects or Transform Patterns on too, and on each copy. This holds on the canvas and in Object › Expand of the fill, for an object's own effects, a fill's or stroke's own, and a group's, where the gradients fitted to its paths, to its own fill, to the groups inside it and to its images' and symbol instances' own fills each fix to their own object's fit. Existing documents with such a Transform effect on fitted-gradient art draw differently: before, the gradient refit to the turned outline. The Gradient tool still shows a fitted gradient's vector at its unturned fit. How gradients follow the effect is VectorCraft's own rule; what the effect does to the object is described in [Distort and transform effects](https://helpx.adobe.com/illustrator/desktop/manage-objects/reshape-transform-objects/distort-and-transform-effects-in-illustrator.html) (effects `bake::tests::a_fitted_gradient_turns_reflects_and_stretches_with_a_transform_effect`, `bake::tests::a_transform_effect_that_scales_to_nothing_leaves_a_fitted_gradient_fitted`, `group::tests::a_groups_transform_turns_the_gradients_fitted_to_its_members_and_its_own_fill`; render `objectfx::a_fitted_gradient_turns_and_reflects_with_its_transform_on_the_canvas`; engine `objexpand::a_fitted_gradient_turned_by_a_transform_expands_as_the_canvas_draws_it`). Scores and hours unchanged.
 - **Placed gradients follow Transform and Free Distort effects:** a gradient placed with the Gradient tool moves, turns and scales with the object when the object's Transform effect moves its outline, and each copy of the Transform effect takes it as many times as it takes the transform. Under Free Distort it moves and scales from the path's bounds before the effect to its bounds after it. This holds on the canvas, in export, in Expand Appearance, in Pathfinder and compound shapes, and in Object › Expand of the fill, for an object's own effects, a group's (the own fills of the group, of the groups inside it, of a symbol's art, and of the images and symbol instances it moves, included) and a fill's or stroke's own. A gradient on a path inside a group with a Transform effect now moves with the path (#2214 moved only the gradients of type), and so does a gradient on an image's or symbol instance's own fill. When a path keeps its shape because the effect would pass the geometry budget, the group's own gradients stay in place; a hidden path in a layer, which the layer's bounds leave out, does not hold them. A freeform gradient whose points were edited moves its points in the same way. How gradients follow each effect is VectorCraft's own rule; what each effect does to the object is described in [Distort and transform effects](https://helpx.adobe.com/illustrator/desktop/manage-objects/reshape-transform-objects/distort-and-transform-effects-in-illustrator.html) (effects `bake::tests::a_baked_transform_moves_a_placed_gradient_with_the_path`, `bake::tests::a_strokes_own_transform_and_free_distort_move_its_placed_gradient`, `bake::tests::a_fills_gradient_follows_the_effects_around_its_transform_with_options`, `bake::tests::baked_free_distort_moves_placed_gradients_from_the_bounds_to_the_distorted_bounds`, `group::tests::a_groups_transform_and_free_distort_move_the_gradients_placed_on_its_paths`, `group::tests::a_groups_transform_moves_the_gradient_of_its_own_fill`, `group::tests::a_nested_groups_own_gradient_follows_the_outer_groups_transform_and_free_distort`, `group::tests::a_groups_transform_moves_the_gradients_placed_on_an_images_own_fills`, `group::tests::shape_art_moves_gradients_with_a_transform_effect`, `group::tests::shape_art_moves_the_gradient_of_a_symbol_instances_art_with_its_transform`, `tests::art_past_the_budget_keeps_its_own_gradients_in_place`, `tests::a_hidden_path_past_the_budget_leaves_a_layers_gradients_free_to_move`, `tests::edited_freeform_points_follow_a_transform_effect_and_free_distort`; render `objectfx::a_paths_gradient_moves_with_its_transform_and_free_distort`; engine `objexpand::a_placed_gradient_moved_by_a_transform_or_free_distort_expands_as_the_canvas_draws_it`). Scores and hours unchanged.- **Constrain Angle (#394):** General › Constrain Angle turns the arrow keys' axes (guides stay on the page's), holds Shift drags of the Selection, Direct Selection, Free Transform, Slice Selection, Reshape and Measure tools and the Pen's handles to the turned axes, and new rectangles, rounded rectangles, ellipses, grids, point and area type, Shift-drawn polygons and stars and the shape size dialogs are drawn along it with their bounding box turned; 0° and whole turns are exactly as before, quarter turns exact (<https://helpx.adobe.com/illustrator/desktop/manage-objects/arrange-objects/rotate-objects-by-specific-angles.html>). Tests: `tests_constrain_tools`, `tests_constrain_new` (engine), `geom` `constrain_axes` / `rotate_deg`, the shape, grid and type tool tests.