feat(tools): Add background tool

docs/ARCHITECTURE.md

@@ -171,6 +171,38 @@ numbers on pictures (`ImageOptions.Annotations`): points are parts of the pictur
 - `AnnotateTool.ConversionOf` (Core) turns the tool into a conversion in the picture's own format (as Pixelate / blur),
   run by the job queue; `ReworksPixels` includes the marks.
 
+## Add background tool
+
+"Add background" (`tool-background`, palette only, settings schema 64) sets pictures on a gradient, a colour or a
+picture of one's own, with padding, rounded corners, a shadow and a canvas shape (`BackdropOptions`). Sizes are parts of
+the picture (padding of its longer side, corners of its shorter side), so a look suits any picture.
+
+- `BackgroundTool.ConversionOf` (Core) turns the tool into a PNG conversion with `ImageOptions.Backdrop`, run by the job
+  queue like Pixelate / blur's areas: `ReworksPixels` includes it, so it is applied once, in the first transform step.
+  The tool keeps the last look apart, in `ImageOptions.BackdropLook`; an export or import leaves out the path of a
+  picture of one's own.
+- `Engines/Magick/BackdropComposer` composes it in `ImageEncoder.ApplyOptions`, after resizing, background removal and
+  grayscale and before the density, metadata and alpha steps. The picture is brought to sRGB as it is seen (through its
+  profile, or by formula for CMYK and grey); the canvas grows round it to the shape (never crops) and stays within a
+  pixel limit (`PictureSizeOn`). It is drawn by Skia as the window draws it: a linear gradient shader, a colour, or
+  one's own picture covering (`ReadPictureBehind`: a raster picture of a few kinds, by extension or by its first bytes,
+  its size checked before it is decoded, read as large as covering the canvas takes and cropped to it, in sRGB, white
+  where see-through; one that can't be read refuses the file); the picture with its corners cut round in its own pixels;
+  Skia's drop shadow of what shows of it, blurred at most at a sigma of 100 (a wider one drawn smaller and scaled up,
+  where Skia's blur stays Gaussian). The canvas is drawn in tiles at most 2048 px wide, a band at a time, as RGB: a blur
+  is never larger than a tile and the shadow's reach round it (a wider shadow is blurred once, scaled down until its
+  sigma is 100 or less). The EXIF thumbnail is dropped.
+- `BackgroundViewModel` draws the same composition live with Avalonia: the layout and shadow from the composer's
+  formulas (an Avalonia drop shadow is Skia's), the picture and the one behind read through the composer's functions,
+  the preview never mirrored in a right-to-left UI. A picture behind is read when it is chosen, and again when it is
+  picked again; Save waits for one that can be read, and one whose file changed since it was read (time written or
+  length) is read again and shown before it is saved. The conversion carries that stamp, and the composer refuses the
+  file (`error.background_picture_changed`, which the toast offers no Retry for) when the picture behind changed since,
+  before it is read or after: a change after Save gives no file rather than one with a picture behind the window didn't
+  show. A change that keeps both the time and the length (a copy that keeps the time, of a picture of the same size)
+  isn't told apart, and the picture itself edited meanwhile isn't looked for (as in Pixelate / blur and Annotate). One
+  look for all pictures or one each; failures end on a summary, as in Pixelate / blur.
+
 ## Crop overlay and PDF page editor
 
 The image Crop tool (`tool-crop`) and PDF Crop (`tool-pdf-crop`) open `Views/CropOverlayWindow` instead of running a job:

src/Filee.App/Assets/i18n/ar.json

@@ -297,6 +297,8 @@
   "preset.hide": "بكسلة / تمويه",
   "preset.hide.donut": "بكسلة",
   "error.cannot_hide": "البكسلة والتمويه متاحان للصور فقط",
+  "error.background_picture": "تعذّرت قراءة الصورة المراد وضعها في الخلفية",
+  "error.background_picture_changed": "تغيّرت الصورة المراد وضعها في الخلفية بعد عرضها. أضف الخلفية مرة أخرى.",
   "hide.save": "إخفاء وحفظ",
   "hide.save_next": "إخفاء والتالي",
   "hide.pixelate": "بكسلة",
@@ -412,6 +414,7 @@
   "preset.rotate_180.short": "180°",
   "preset.group_flip": "انعكاس",
   "preset.annotate": "تعليقات",
+  "preset.background": "إضافة خلفية",
   "preset.flip_horizontal": "انعكاس أفقي",
   "preset.flip_horizontal.short": "أفقي",
   "preset.flip_vertical": "انعكاس عمودي",
@@ -1006,6 +1009,43 @@
   "annotate.keys": "V للتحديد · Tab لاختيار علامة والأسهم لتحريكها · P A B H T N لاختيار أداة · Del للإزالة · Ctrl+Z للتراجع · Esc للإغلاق",
   "annotate.save": "حفظ",
   "annotate.save_next": "حفظ والتالي",
+  "background.background": "الخلفية",
+  "background.gradient": "تدرّج",
+  "background.color": "لون",
+  "background.picture": "صورة",
+  "background.from": "اللون الأول",
+  "background.to": "اللون الثاني",
+  "background.choose": "اختيار…",
+  "background.no_picture": "لم تُختر صورة",
+  "background.padding": "الهامش",
+  "background.corners": "الزوايا",
+  "background.shadow": "الظل",
+  "background.shadow_none": "بلا",
+  "background.shadow_light": "خفيف",
+  "background.shadow_soft": "ناعم",
+  "background.shadow_strong": "قوي",
+  "background.canvas": "اللوحة",
+  "background.auto": "تلقائي",
+  "background.square": "مربع",
+  "background.landscape": "أفقي (16:9)",
+  "background.portrait": "عمودي (4:5)",
+  "background.same_look": "المظهر نفسه لكل الصور",
+  "background.save": "حفظ",
+  "background.save_next": "حفظ والتالي",
+  "background.gradient_sunset": "غروب",
+  "background.gradient_sky": "سماء",
+  "background.gradient_mint": "نعناع",
+  "background.gradient_peach": "خوخ",
+  "background.gradient_ocean": "محيط",
+  "background.gradient_lilac": "ليلكي",
+  "background.color_white": "أبيض",
+  "background.color_paper": "ورقي",
+  "background.color_charcoal": "فحمي",
+  "background.color_navy": "كحلي",
+  "background.color_sand": "رملي",
+  "background.color_sage": "مريمية",
+  "background.picture_unreadable": "تعذّرت قراءة هذه الصورة. اختر صورة أخرى، أو تدرّجًا أو لونًا.",
+  "background.keys": "Enter يحفظ · Esc يغلق · Tab يتنقّل بين خيارات المظهر · الأسهم تختار أو تحرّك شريط التمرير",
   "presets.editor_title": "تعديل الإعداد المسبق",
   "presets.delete_confirm": "هل تريد حذف «{0}»؟ سيُزال أيضًا من جميع أشرطة الأدوات والمجموعات.",
   "presets.name_required": "أدخل اسمًا",

src/Filee.App/Assets/i18n/de.json

@@ -297,6 +297,8 @@
   "preset.hide": "Verpixeln / Weichzeichnen",
   "preset.hide.donut": "Verpixeln",
   "error.cannot_hide": "Verpixeln und Weichzeichnen ist nur bei Bildern möglich",
+  "error.background_picture": "Das Bild für den Hintergrund kann nicht gelesen werden",
+  "error.background_picture_changed": "Das Bild für den Hintergrund hat sich geändert, nachdem es angezeigt wurde. Füge den Hintergrund noch einmal hinzu.",
   "hide.save": "Verbergen & Speichern",
   "hide.save_next": "Verbergen & Weiter",
   "hide.pixelate": "Verpixeln",
@@ -412,6 +414,7 @@
   "preset.rotate_180.short": "180°",
   "preset.group_flip": "Spiegeln",
   "preset.annotate": "Beschriften",
+  "preset.background": "Hintergrund hinzufügen",
   "preset.flip_horizontal": "Horizontal spiegeln",
   "preset.flip_horizontal.short": "Horizontal",
   "preset.flip_vertical": "Vertikal spiegeln",
@@ -1006,6 +1009,43 @@
   "annotate.keys": "V wählt aus · Tab wählt eine Markierung, Pfeiltasten verschieben sie · P A B H T N wählen ein Werkzeug · Entf entfernt · Strg+Z macht rückgängig · Esc schließt",
   "annotate.save": "Speichern",
   "annotate.save_next": "Speichern & weiter",
+  "background.background": "Hintergrund",
+  "background.gradient": "Verlauf",
+  "background.color": "Farbe",
+  "background.picture": "Bild",
+  "background.from": "Erste Farbe",
+  "background.to": "Zweite Farbe",
+  "background.choose": "Auswählen…",
+  "background.no_picture": "Kein Bild ausgewählt",
+  "background.padding": "Abstand",
+  "background.corners": "Ecken",
+  "background.shadow": "Schatten",
+  "background.shadow_none": "Keiner",
+  "background.shadow_light": "Leicht",
+  "background.shadow_soft": "Weich",
+  "background.shadow_strong": "Stark",
+  "background.canvas": "Leinwand",
+  "background.auto": "Automatisch",
+  "background.square": "Quadrat",
+  "background.landscape": "Querformat (16:9)",
+  "background.portrait": "Hochformat (4:5)",
+  "background.same_look": "Gleicher Look für alle Bilder",
+  "background.save": "Speichern",
+  "background.save_next": "Speichern & weiter",
+  "background.gradient_sunset": "Sonnenuntergang",
+  "background.gradient_sky": "Himmel",
+  "background.gradient_mint": "Minze",
+  "background.gradient_peach": "Pfirsich",
+  "background.gradient_ocean": "Ozean",
+  "background.gradient_lilac": "Flieder",
+  "background.color_white": "Weiß",
+  "background.color_paper": "Papier",
+  "background.color_charcoal": "Anthrazit",
+  "background.color_navy": "Marineblau",
+  "background.color_sand": "Sand",
+  "background.color_sage": "Salbei",
+  "background.picture_unreadable": "Dieses Bild kann nicht gelesen werden. Wähle ein anderes, einen Verlauf oder eine Farbe.",
+  "background.keys": "Eingabe speichert · Esc schließt · Tab geht durch den Look · Pfeiltasten wählen oder bewegen einen Regler",
   "presets.editor_title": "Vorlage bearbeiten",
   "presets.delete_confirm": "„{0}“ löschen? Die Vorlage wird auch aus allen Werkzeugleisten und Gruppen entfernt.",
   "presets.name_required": "Namen eingeben",

src/Filee.App/Assets/i18n/en.json

@@ -306,6 +306,8 @@
   "preset.hide": "Pixelate / blur",
   "preset.hide.donut": "Pixelate",
   "error.cannot_hide": "Only pictures can be pixelated or blurred",
+  "error.background_picture": "The picture to put behind can't be read",
+  "error.background_picture_changed": "The picture to put behind changed after it was shown. Add the background again.",
   "hide.save": "Hide & Save",
   "hide.save_next": "Hide & Next",
   "hide.pixelate": "Pixelate",
@@ -422,6 +424,7 @@
   "preset.rotate_180.short": "180°",
   "preset.group_flip": "Flip",
   "preset.annotate": "Annotate",
+  "preset.background": "Add background",
   "preset.flip_horizontal": "Flip horizontal",
   "preset.flip_horizontal.short": "Horizontal",
   "preset.flip_vertical": "Flip vertical",
@@ -1021,6 +1024,43 @@
   "annotate.keys": "V selects · Tab picks a mark, arrows move it · P A B H T N pick a tool · Del removes · Ctrl+Z undoes · Esc closes",
   "annotate.save": "Save",
   "annotate.save_next": "Save & next",
+  "background.background": "Background",
+  "background.gradient": "Gradient",
+  "background.color": "Colour",
+  "background.picture": "Picture",
+  "background.from": "First colour",
+  "background.to": "Second colour",
+  "background.choose": "Choose…",
+  "background.no_picture": "No picture chosen",
+  "background.padding": "Padding",
+  "background.corners": "Corners",
+  "background.shadow": "Shadow",
+  "background.shadow_none": "None",
+  "background.shadow_light": "Light",
+  "background.shadow_soft": "Soft",
+  "background.shadow_strong": "Strong",
+  "background.canvas": "Canvas",
+  "background.auto": "Auto",
+  "background.square": "Square",
+  "background.landscape": "Landscape (16:9)",
+  "background.portrait": "Portrait (4:5)",
+  "background.same_look": "Same look for all pictures",
+  "background.save": "Save",
+  "background.save_next": "Save & next",
+  "background.gradient_sunset": "Sunset",
+  "background.gradient_sky": "Sky",
+  "background.gradient_mint": "Mint",
+  "background.gradient_peach": "Peach",
+  "background.gradient_ocean": "Ocean",
+  "background.gradient_lilac": "Lilac",
+  "background.color_white": "White",
+  "background.color_paper": "Paper",
+  "background.color_charcoal": "Charcoal",
+  "background.color_navy": "Navy",
+  "background.color_sand": "Sand",
+  "background.color_sage": "Sage",
+  "background.picture_unreadable": "This picture can't be read. Choose another one, or a gradient or a colour.",
+  "background.keys": "Enter saves · Esc closes · Tab goes through the look · arrows choose or move a slider",
   "presets.editor_title": "Edit preset",
   "presets.delete_confirm": "Delete “{0}”? It will also be removed from every toolbar and group.",
   "presets.name_required": "Enter a name",

src/Filee.App/Assets/i18n/es.json

@@ -297,6 +297,8 @@
   "preset.hide": "Pixelar / difuminar",
   "preset.hide.donut": "Pixelar",
   "error.cannot_hide": "Solo se pueden pixelar o difuminar imágenes",
+  "error.background_picture": "No se puede leer la imagen para el fondo",
+  "error.background_picture_changed": "La imagen para el fondo cambió después de mostrarse. Vuelve a añadir el fondo.",
   "hide.save": "Ocultar y guardar",
   "hide.save_next": "Ocultar y seguir",
   "hide.pixelate": "Pixelar",
@@ -412,6 +414,7 @@
   "preset.rotate_180.short": "180°",
   "preset.group_flip": "Voltear",
   "preset.annotate": "Anotar",
+  "preset.background": "Añadir fondo",
   "preset.flip_horizontal": "Volteo horizontal",
   "preset.flip_horizontal.short": "Horizontal",
   "preset.flip_vertical": "Volteo vertical",
@@ -1006,6 +1009,43 @@
   "annotate.keys": "V selecciona · Tab elige una marca, las flechas la mueven · P A B H T N eligen herramienta · Supr quita · Ctrl+Z deshace · Esc cierra",
   "annotate.save": "Guardar",
   "annotate.save_next": "Guardar y siguiente",
+  "background.background": "Fondo",
+  "background.gradient": "Degradado",
+  "background.color": "Color",
+  "background.picture": "Imagen",
+  "background.from": "Primer color",
+  "background.to": "Segundo color",
+  "background.choose": "Elegir…",
+  "background.no_picture": "No se ha elegido imagen",
+  "background.padding": "Margen",
+  "background.corners": "Esquinas",
+  "background.shadow": "Sombra",
+  "background.shadow_none": "Ninguna",
+  "background.shadow_light": "Ligera",
+  "background.shadow_soft": "Suave",
+  "background.shadow_strong": "Fuerte",
+  "background.canvas": "Lienzo",
+  "background.auto": "Auto",
+  "background.square": "Cuadrado",
+  "background.landscape": "Horizontal (16:9)",
+  "background.portrait": "Vertical (4:5)",
+  "background.same_look": "Mismo aspecto para todas las imágenes",
+  "background.save": "Guardar",
+  "background.save_next": "Guardar y siguiente",
+  "background.gradient_sunset": "Atardecer",
+  "background.gradient_sky": "Cielo",
+  "background.gradient_mint": "Menta",
+  "background.gradient_peach": "Melocotón",
+  "background.gradient_ocean": "Océano",
+  "background.gradient_lilac": "Lila",
+  "background.color_white": "Blanco",
+  "background.color_paper": "Papel",
+  "background.color_charcoal": "Carbón",
+  "background.color_navy": "Azul marino",
+  "background.color_sand": "Arena",
+  "background.color_sage": "Salvia",
+  "background.picture_unreadable": "No se puede leer esta imagen. Elige otra, o un degradado o un color.",
+  "background.keys": "Intro guarda · Esc cierra · Tab recorre el aspecto · las flechas eligen o mueven un control deslizante",
   "presets.editor_title": "Editar ajuste preestablecido",
   "presets.delete_confirm": "¿Eliminar «{0}»? También se quitará de todos los menús circulares y grupos.",
   "presets.name_required": "Escribe un nombre",

src/Filee.App/Assets/i18n/fr.json

@@ -306,6 +306,8 @@
   "preset.hide": "Pixeliser / flouter",
   "preset.hide.donut": "Pixeliser",
   "error.cannot_hide": "Seules les images peuvent être pixelisées ou floutées",
+  "error.background_picture": "Impossible de lire l'image à mettre en arrière-plan",
+  "error.background_picture_changed": "L'image à mettre en arrière-plan a changé après avoir été affichée. Ajoutez de nouveau l'arrière-plan.",
   "hide.save": "Masquer et enregistrer",
   "hide.save_next": "Masquer et suivant",
   "hide.pixelate": "Pixeliser",
@@ -422,6 +424,7 @@
   "preset.rotate_180.short": "180°",
   "preset.group_flip": "Retourner",
   "preset.annotate": "Annoter",
+  "preset.background": "Ajouter un fond",
   "preset.flip_horizontal": "Retourner horizontalement",
   "preset.flip_horizontal.short": "Horizontal",
   "preset.flip_vertical": "Retourner verticalement",
@@ -1021,6 +1024,43 @@
   "annotate.keys": "V sélectionne · Tab choisit une marque, les flèches la déplacent · P A B H T N choisissent un outil · Suppr supprime · Ctrl+Z annule · Échap ferme",
   "annotate.save": "Enregistrer",
   "annotate.save_next": "Enregistrer et suivant",
+  "background.background": "Fond",
+  "background.gradient": "Dégradé",
+  "background.color": "Couleur",
+  "background.picture": "Image",
+  "background.from": "Première couleur",
+  "background.to": "Deuxième couleur",
+  "background.choose": "Choisir…",
+  "background.no_picture": "Aucune image choisie",
+  "background.padding": "Marge",
+  "background.corners": "Coins",
+  "background.shadow": "Ombre",
+  "background.shadow_none": "Aucune",
+  "background.shadow_light": "Légère",
+  "background.shadow_soft": "Douce",
+  "background.shadow_strong": "Forte",
+  "background.canvas": "Toile",
+  "background.auto": "Auto",
+  "background.square": "Carré",
+  "background.landscape": "Paysage (16:9)",
+  "background.portrait": "Portrait (4:5)",
+  "background.same_look": "Même apparence pour toutes les images",
+  "background.save": "Enregistrer",
+  "background.save_next": "Enregistrer et suivant",
+  "background.gradient_sunset": "Coucher de soleil",
+  "background.gradient_sky": "Ciel",
+  "background.gradient_mint": "Menthe",
+  "background.gradient_peach": "Pêche",
+  "background.gradient_ocean": "Océan",
+  "background.gradient_lilac": "Lilas",
+  "background.color_white": "Blanc",
+  "background.color_paper": "Papier",
+  "background.color_charcoal": "Anthracite",
+  "background.color_navy": "Bleu marine",
+  "background.color_sand": "Sable",
+  "background.color_sage": "Sauge",
+  "background.picture_unreadable": "Impossible de lire cette image. Choisissez-en une autre, ou un dégradé ou une couleur.",
+  "background.keys": "Entrée enregistre · Échap ferme · Tab parcourt l'apparence · les flèches choisissent ou déplacent un curseur",
   "presets.editor_title": "Modifier le préréglage",
   "presets.delete_confirm": "Supprimer « {0} » ? Il sera aussi retiré de tous les menus circulaires et groupes.",
   "presets.name_required": "Saisissez un nom",