using System;
using System.IO;
using Atalasoft.Imaging;
using Atalasoft.Imaging.ImageSources;
using System.Drawing;
using System.Collections.Generic;
using Atalasoft.Imaging.Codec.Pdf;

namespace AtalasoftSupportUtils
{
    // in this class, we are subclassing PdfImageSource and adding some post processing to properly calculate the image resolution
    // this is needed because the PdfImageSource fails to properly report the resolution of extracted files
    //
    public class PdfAccurateResolutionFixImageSource : PdfImageSource
    {
        private List<SizeF> _sizes = new List<SizeF>();


        public PdfAccurateResolutionFixImageSource(Stream stm)
            : base(stm)
        {
            PopulateSizes(stm, null);
        }
        public PdfAccurateResolutionFixImageSource(Stream stm, string password)
            : base(stm, password)
        {
            PopulateSizes(stm, password);
        }

        // this method overrides the LowLevelAcquireMethod in PdfImageSource
        // It lets PdfImageSource get the image (possibly extracting it directly if it's a single
        // image page, then we calculate the iamge resolution and also 
        // try to cut the image bit from 32Bpp to 24 if applicable
        protected override ImageSourceNode LowLevelAcquire(int index)
        {
            ImageSourceNode node = base.LowLevelAcquire(index);
            if (node == null) return null;

            node.Image.Resolution = CalcResValue(node.Image.Size.Width, node.Image.Size.Height, this._sizes[node.Index]);

            // ALSO taking the trouble to reduce image from 32bppBgra to 24bppBgr to make for smaller ouput
            AtalaImage image = null;
            if (node.Image.PixelFormat == PixelFormat.Pixel32bppBgra || node.Image.PixelFormat == PixelFormat.Pixel32bppBgr || node.Image.PixelFormat == PixelFormat.Pixel48bppBgr)
            {
                image = node.Image.GetChangedPixelFormat(PixelFormat.Pixel24bppBgr);
            }

            // couldn't reduce
            if (image == null) return node;

            // don't need original image anymore
            node.Image.Dispose();
            node.Dispose(); //disposes node.reloader. By some reason, this method doesn't dispose the node.image too.
            return new ImageSourceNode(image, new FileReloader(image));
        }

        private Dpi CalcResValue(double imgWidth, double imgHeight, SizeF pgSize)
        {
            return new Dpi((72 * imgWidth / pgSize.Width),(72 * imgHeight / pgSize.Height), ResolutionUnit.DotsPerInch);
        }

        private void PopulateSizes(Stream stm, string password)
        {
            stm.Seek(0, SeekOrigin.Begin);
            Document d = new Document(stm, password);
            foreach (Page p in d.Pages)
            {
                this._sizes.Add(new SizeF((float)p.Width, (float)p.Height));
            }
            d.Dispose();
            stm.Seek(0, SeekOrigin.Begin);
        }
    }
}