unipdf/creator/image.go

/*
 * This file is subject to the terms and conditions defined in
 * file 'LICENSE.md', which is part of this source code package.
 */

package creator

import (
	"bytes"
	"fmt"
	goimage "image"
	"os"

	"github.com/unidoc/unipdf/v3/common"
	"github.com/unidoc/unipdf/v3/contentstream"
	"github.com/unidoc/unipdf/v3/contentstream/draw"
	"github.com/unidoc/unipdf/v3/core"
	"github.com/unidoc/unipdf/v3/model"
)

// The Image type is used to draw an image onto PDF.
type Image struct {
	xobj *model.XObjectImage
	img  *model.Image

	// Rotation angle.
	angle float64

	// The dimensions of the image. As to be placed on the PDF.
	width, height float64

	// The original dimensions of the image (pixel based).
	origWidth, origHeight float64

	// Positioning: relative / absolute.
	positioning positioning

	// Image horizontal alignment in relative positioning.
	hAlignment HorizontalAlignment

	// Absolute coordinates (when in absolute mode).
	xPos float64
	yPos float64

	// Opacity (alpha value).
	opacity float64

	// Margins to be applied around the block when drawing on Page.
	margins margins

	// Rotional origin.  Default (0,0 - upper left corner of block).
	rotOriginX, rotOriginY float64

	// Encoder
	encoder core.StreamEncoder
}

// newImage create a new image from a unidoc image (model.Image).
func newImage(img *model.Image) (*Image, error) {
	// Image original size in points = pixel size.
	width := float64(img.Width)
	height := float64(img.Height)

	return &Image{
		img:         img,
		origWidth:   width,
		origHeight:  height,
		width:       width,
		height:      height,
		angle:       0,
		opacity:     1.0,
		positioning: positionRelative,
	}, nil
}

// newImageFromData creates an Image from image data.
func newImageFromData(data []byte) (*Image, error) {
	imgReader := bytes.NewReader(data)

	// Load the image with default handler.
	img, err := model.ImageHandling.Read(imgReader)
	if err != nil {
		common.Log.Error("Error loading image: %s", err)
		return nil, err
	}

	return newImage(img)
}

// newImageFromFile creates an Image from a file.
func newImageFromFile(path string) (*Image, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	// Load the image with default handler.
	img, err := model.ImageHandling.Read(f)
	if err != nil {
		common.Log.Error("Error loading image: %s", err)
		return nil, err
	}

	return newImage(img)
}

// newImageFromGoImage creates an Image from a go image.Image data structure.
func newImageFromGoImage(goimg goimage.Image) (*Image, error) {
	img, err := model.ImageHandling.NewImageFromGoImage(goimg)
	if err != nil {
		return nil, err
	}

	return newImage(img)
}

// SetEncoder sets the encoding/compression mechanism for the image.
func (img *Image) SetEncoder(encoder core.StreamEncoder) {
	img.encoder = encoder
}

// Height returns Image's document height.
func (img *Image) Height() float64 {
	return img.height
}

// Width returns Image's document width.
func (img *Image) Width() float64 {
	return img.width
}

// SetOpacity sets opacity for Image.
func (img *Image) SetOpacity(opacity float64) {
	img.opacity = opacity
}

// GetHorizontalAlignment returns the horizontal alignment of the image.
func (img *Image) GetHorizontalAlignment() HorizontalAlignment {
	return img.hAlignment
}

// SetHorizontalAlignment sets the horizontal alignment of the image.
func (img *Image) SetHorizontalAlignment(alignment HorizontalAlignment) {
	img.hAlignment = alignment
}

// SetMargins sets the margins for the Image (in relative mode): left, right, top, bottom.
func (img *Image) SetMargins(left, right, top, bottom float64) {
	img.margins.left = left
	img.margins.right = right
	img.margins.top = top
	img.margins.bottom = bottom
}

// GetMargins returns the Image's margins: left, right, top, bottom.
func (img *Image) GetMargins() (float64, float64, float64, float64) {
	return img.margins.left, img.margins.right, img.margins.top, img.margins.bottom
}

// makeXObject makes the encoded XObject Image that will be used in the PDF.
func (img *Image) makeXObject() error {
	encoder := img.encoder
	if encoder == nil {
		// Default: Use flate encoder.
		encoder = core.NewFlateEncoder()
	}

	// Create the XObject image.
	ximg, err := model.NewXObjectImageFromImage(img.img, nil, encoder)
	if err != nil {
		common.Log.Error("Failed to create xobject image: %s", err)
		return err
	}

	img.xobj = ximg
	return nil
}

// GeneratePageBlocks generate the Page blocks. Draws the Image on a block, implementing the Drawable interface.
func (img *Image) GeneratePageBlocks(ctx DrawContext) ([]*Block, DrawContext, error) {
	if img.xobj == nil {
		// Build the XObject Image if not already prepared.
		img.makeXObject()
	}

	var blocks []*Block
	origCtx := ctx

	blk := NewBlock(ctx.PageWidth, ctx.PageHeight)
	if img.positioning.isRelative() {
		if img.height > ctx.Height {
			// Goes out of the bounds.  Write on a new template instead and create a new context at upper
			// left corner.

			blocks = append(blocks, blk)
			blk = NewBlock(ctx.PageWidth, ctx.PageHeight)

			// New Page.
			ctx.Page++
			newContext := ctx
			newContext.Y = ctx.Margins.top // + p.Margins.top
			newContext.X = ctx.Margins.left + img.margins.left
			newContext.Height = ctx.PageHeight - ctx.Margins.top - ctx.Margins.bottom - img.margins.bottom
			newContext.Width = ctx.PageWidth - ctx.Margins.left - ctx.Margins.right - img.margins.left - img.margins.right
			ctx = newContext
		} else {
			ctx.Y += img.margins.top
			ctx.Height -= img.margins.top + img.margins.bottom
			ctx.X += img.margins.left
			ctx.Width -= img.margins.left + img.margins.right
		}
	} else {
		// Absolute.
		ctx.X = img.xPos
		ctx.Y = img.yPos
	}

	// Place the Image on the template at position (x,y) based on the ctx.
	ctx, err := drawImageOnBlock(blk, img, ctx)
	if err != nil {
		return nil, ctx, err
	}

	blocks = append(blocks, blk)

	if img.positioning.isAbsolute() {
		// Absolute drawing should not affect context.
		ctx = origCtx
	} else {
		// TODO: Use projected height.
		ctx.Y += img.margins.bottom
		ctx.Height -= img.margins.bottom
	}

	return blocks, ctx, nil
}

// SetPos sets the absolute position. Changes object positioning to absolute.
func (img *Image) SetPos(x, y float64) {
	img.positioning = positionAbsolute
	img.xPos = x
	img.yPos = y
}

// Scale scales Image by a constant factor, both width and height.
func (img *Image) Scale(xFactor, yFactor float64) {
	img.width = xFactor * img.width
	img.height = yFactor * img.height
}

// ScaleToWidth scale Image to a specified width w, maintaining the aspect ratio.
func (img *Image) ScaleToWidth(w float64) {
	ratio := img.height / img.width
	img.width = w
	img.height = w * ratio
}

// ScaleToHeight scale Image to a specified height h, maintaining the aspect ratio.
func (img *Image) ScaleToHeight(h float64) {
	ratio := img.width / img.height
	img.height = h
	img.width = h * ratio
}

// SetWidth set the Image's document width to specified w. This does not change the raw image data, i.e.
// no actual scaling of data is performed. That is handled by the PDF viewer.
func (img *Image) SetWidth(w float64) {
	img.width = w
}

// SetHeight sets the Image's document height to specified h.
func (img *Image) SetHeight(h float64) {
	img.height = h
}

// SetAngle sets Image rotation angle in degrees.
func (img *Image) SetAngle(angle float64) {
	img.angle = angle
}

// rotatedSize returns the width and height of the rotated image bounding box.
func (img *Image) rotatedSize() (float64, float64) {
	width := img.width
	height := img.height
	angle := img.angle

	if angle == 0 {
		return width, height
	}

	// Get rotated size
	bbox := draw.Path{Points: []draw.Point{
		draw.NewPoint(0, 0).Rotate(angle),
		draw.NewPoint(width, 0).Rotate(angle),
		draw.NewPoint(0, height).Rotate(angle),
		draw.NewPoint(width, height).Rotate(angle),
	}}.GetBoundingBox()

	return bbox.Width, bbox.Height
}

// Draw the image onto the specified blk.
func drawImageOnBlock(blk *Block, img *Image, ctx DrawContext) (DrawContext, error) {
	origCtx := ctx

	// Find a free name for the image.
	num := 1
	imgName := core.PdfObjectName(fmt.Sprintf("Img%d", num))
	for blk.resources.HasXObjectByName(imgName) {
		num++
		imgName = core.PdfObjectName(fmt.Sprintf("Img%d", num))
	}

	// Add to the Page resources.
	err := blk.resources.SetXObjectImageByName(imgName, img.xobj)
	if err != nil {
		return ctx, err
	}

	// Find an available GS name.
	i := 0
	gsName := core.PdfObjectName(fmt.Sprintf("GS%d", i))
	for blk.resources.HasExtGState(gsName) {
		i++
		gsName = core.PdfObjectName(fmt.Sprintf("GS%d", i))
	}

	// Graphics state with normal blend mode.
	gs0 := core.MakeDict()
	gs0.Set("BM", core.MakeName("Normal"))
	if img.opacity < 1.0 {
		gs0.Set("CA", core.MakeFloat(img.opacity))
		gs0.Set("ca", core.MakeFloat(img.opacity))
	}

	err = blk.resources.AddExtGState(gsName, core.MakeIndirectObject(gs0))
	if err != nil {
		return ctx, err
	}

	width := img.Width()
	height := img.Height()
	_, rotatedHeight := img.rotatedSize()

	// Calculate x coordinate based on the image alignment.
	xPos := ctx.X
	yPos := ctx.PageHeight - ctx.Y - height
	if img.positioning.isRelative() {
		yPos -= (rotatedHeight - height) / 2

		switch img.hAlignment {
		case HorizontalAlignmentCenter:
			xPos += (ctx.Width - width) / 2
		case HorizontalAlignmentRight:
			xPos = ctx.PageWidth - ctx.Margins.right - img.margins.right - width
		}
	}
	angle := img.angle

	// Create content stream to add to the Page contents.
	contentCreator := contentstream.NewContentCreator()

	// Set graphics state.
	contentCreator.Add_gs(gsName)

	contentCreator.Translate(xPos, yPos)
	if angle != 0 {
		// Make rotation origin the center of the image.
		contentCreator.Translate(width/2, height/2)
		contentCreator.RotateDeg(angle)
		contentCreator.Translate(-width/2, -height/2)
	}

	// Draw the image.
	contentCreator.Scale(width, height).Add_Do(imgName)

	ops := contentCreator.Operations()
	ops.WrapIfNeeded()

	blk.addContents(ops)

	if img.positioning.isRelative() {
		ctx.Y += rotatedHeight
		ctx.Height -= rotatedHeight
		return ctx, nil
	}

	// Absolute positioning - return original context.
	return origCtx, nil
}