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// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ofdgo
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import (
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"context"
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"fmt"
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"math"
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)
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// WatermarkOptions 配置水印旋转、居中和平铺，Area为页面比例区域，nil使用整页
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// Angle为顺时针角度，Gap为平铺最小毫米间距，零值使用10毫米
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// 非平铺时Area宽高同时为零表示中心点定位，不缩放图元
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type WatermarkOptions struct {
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Creator string
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Angle float64
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Tile bool
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Area *Box
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Gap float64
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}
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// AddWatermarks 向指定页面添加文字或图片水印，复用编辑器字体来源及后端，一次操作计入一条撤销记录
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// 图元Boundary提供原始尺寸，忽略其位置；按实际绘制范围居中，超出区域时等比缩小
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// 失败或取消时保留原文档，输入图元不被修改
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// 入参: ctx 取消上下文, indexes 不重复的页面索引, object 水印图元, options 布局选项
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// 返回: []string 按页面顺序排列的注解标识, error 错误信息
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func (e *Editor) AddWatermarks(ctx context.Context, indexes []int, object GraphicObject, options WatermarkOptions) ([]string, error) {
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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if err := e.validatePageIndexes(indexes); err != nil {
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return nil, err
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}
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if !finite(options.Angle) || !finite(options.Gap) || options.Gap < 0 {
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return nil, fmt.Errorf("invalid watermark angle or gap")
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}
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if area := options.Area; area != nil {
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point := !options.Tile && area.W == 0 && area.H == 0
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if !finite(area.X) || !finite(area.Y) || !finite(area.W) || !finite(area.H) || area.X < 0 || area.Y < 0 || (!point && (area.W <= 0 || area.H <= 0)) || area.X+area.W > 1 || area.Y+area.H > 1 {
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return nil, fmt.Errorf("invalid watermark area")
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}
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}
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if options.Gap == 0 {
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options.Gap = 10
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}
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object = cloneEditorData(object)
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var boundary, ctm *string
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switch object.Type {
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case "TextObject":
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boundary, ctm = &object.TextObject.Boundary, &object.TextObject.CTM
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case "ImageObject":
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boundary, ctm = &object.ImageObject.Boundary, &object.ImageObject.CTM
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default:
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return nil, fmt.Errorf("watermark requires text or image")
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}
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box, err := creationBox(*boundary)
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if err != nil || box.W <= 0 || box.H <= 0 {
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return nil, fmt.Errorf("invalid watermark dimensions")
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}
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if len(indexes) == 0 {
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return nil, nil
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}
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box.X, box.Y = 0, 0
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*boundary = editorBoxString(box)
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angle := math.Mod(options.Angle, 360) * math.Pi / 180
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rotation := Matrix{a: math.Cos(angle), b: math.Sin(angle), c: -math.Sin(angle), d: math.Cos(angle)}
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rotation = TranslationMatrix(box.W/2, box.H/2).Multiply(rotation).Multiply(TranslationMatrix(-box.W/2, -box.H/2))
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if *ctm != "" {
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if _, err := creationNumbers(*ctm, 6); err != nil {
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return nil, err
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}
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} else if object.Type == "ImageObject" {
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*ctm = (Matrix{a: box.W, d: box.H}).String()
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}
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*ctm = rotation.Multiply(NewMatrix(*ctm)).String()
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preview := e.transactionSnapshot()
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preview.SetHistoryLimit(0)
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id, err := preview.AddObject(indexes[0], object)
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if err != nil {
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return nil, err
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}
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object, err = preview.Object(indexes[0], id)
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if err != nil {
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return nil, err
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}
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reader, err := preview.Reader()
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if err != nil {
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return nil, err
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}
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defer reader.Close()
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page, err := reader.PageContentByIndex(indexes[0])
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if err != nil {
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return nil, err
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}
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renderer := e.newRenderer(reader)
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measured := cloneEditorData(object)
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if measured.Type == "TextObject" {
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measured.TextObject.Alpha = nil
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} else {
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measured.ImageObject.Alpha = nil
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}
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bounds, err := renderer.ObjectBounds(measured, "")
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if err != nil {
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return nil, err
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}
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if !finite(bounds.X) || !finite(bounds.Y) || !finite(bounds.W) || !finite(bounds.H) || bounds.W <= 0 || bounds.H <= 0 {
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return nil, fmt.Errorf("watermark has no visible content")
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}
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var ids []string
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err = e.Transaction(func(edit *Editor) error {
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for _, index := range indexes {
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if err := ctx.Err(); err != nil {
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return err
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}
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if index != indexes[0] {
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page, err = reader.PageContentByIndex(index)
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if err != nil {
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return err
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}
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}
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pageBox, err := renderer.GetPageBox(page)
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if err != nil {
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return err
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}
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annotation, err := layoutWatermark(ctx, object, bounds, box, options, pageBox)
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if err != nil {
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return err
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}
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id, err := edit.AddAnnotation(index, annotation)
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if err != nil {
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return err
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}
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ids = append(ids, id)
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}
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return ctx.Err()
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})
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if err != nil {
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return nil, err
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}
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return ids, nil
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}
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// layoutWatermark 按绘制范围布局独立水印外观，保留页面原点及图元变换
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// 入参: ctx 取消上下文, base 水印图元, bounds 绘制范围, box 原始尺寸, options 布局选项, page 页面范围
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// 返回: Annotation 水印注解, error 取消或布局错误
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func layoutWatermark(ctx context.Context, base GraphicObject, bounds, box Box, options WatermarkOptions, page Box) (Annotation, error) {
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area := page
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if options.Area != nil {
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area = Box{X: page.X + options.Area.X*page.W, Y: page.Y + options.Area.Y*page.H, W: options.Area.W * page.W, H: options.Area.H * page.H}
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}
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if !finite(page.X) || !finite(page.Y) || !finite(page.W) || !finite(page.H) || page.W <= 0 || page.H <= 0 {
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return Annotation{}, fmt.Errorf("invalid watermark page area")
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}
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scale := 1.0
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if area.W > 0 && area.H > 0 {
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scale = math.Min(1, math.Min(area.W/bounds.W, area.H/bounds.H))
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}
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if scale != 1 {
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matrix := Matrix{a: scale, d: scale}
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if base.Type == "TextObject" {
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base.TextObject.CTM = matrix.Multiply(NewMatrix(base.TextObject.CTM)).String()
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} else {
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base.ImageObject.CTM = matrix.Multiply(NewMatrix(base.ImageObject.CTM)).String()
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}
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bounds = matrix.TransformBox(bounds)
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}
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columns, rows := 1.0, 1.0
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if options.Tile {
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angle := math.Mod(options.Angle, 360) * math.Pi / 180
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width := math.Max(bounds.W, (math.Abs(math.Cos(angle))*box.W+math.Abs(math.Sin(angle))*box.H)*scale)
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height := math.Max(bounds.H, (math.Abs(math.Sin(angle))*box.W+math.Abs(math.Cos(angle))*box.H)*scale)
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columns = math.Max(1, math.Floor((area.W+options.Gap)/(width+options.Gap)))
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rows = math.Max(1, math.Floor((area.H+options.Gap)/(height+options.Gap)))
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} else {
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area = Box{X: area.X + (area.W-bounds.W)/2, Y: area.Y + (area.H-bounds.H)/2, W: bounds.W, H: bounds.H}
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}
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if !finite(columns*rows) || columns*rows > 100000 {
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return Annotation{}, fmt.Errorf("too many watermark tiles")
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}
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annotation := Annotation{Type: "Watermark", Creator: options.Creator, Appearance: Appearance{Boundary: editorBoxString(area)}}
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annotation.Appearance.Objects = make([]GraphicObject, 0, int(columns*rows))
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for row := 0; row < int(rows); row++ {
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if err := ctx.Err(); err != nil {
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return Annotation{}, err
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}
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for column := 0; column < int(columns); column++ {
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x := (float64(column)+0.5)*area.W/columns - bounds.X - bounds.W/2
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y := (float64(row)+0.5)*area.H/rows - bounds.Y - bounds.H/2
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object := base
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boundary := editorBoxString(Box{X: x, Y: y, W: box.W, H: box.H})
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if object.Type == "TextObject" {
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object.TextObject.Boundary = boundary
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} else {
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object.ImageObject.Boundary = boundary
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}
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annotation.Appearance.Objects = append(annotation.Appearance.Objects, object)
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}
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}
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return annotation, nil
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}
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