PngWriter Class

Syntax

Public NotInheritable Class PngWriter _
	Inherits FormatWriter

public sealed class PngWriter : FormatWriter

Remarks

The Portable Network Graphics (PNG) format was designed to replace the older and simpler GIF format and, to some extent, the much more complex TIFF format. Besides of it, PNG was developed to avoid legal problems which was caused by LZW algorithm used in GIF and sometimes in TIFF. For the Web, PNG really has four main advantages over GIF:

• Alpha channel support (variable transparency);Gamma correction (cross-platform control of image brightness);Two-dimensional interlacing (a method of progressive display);In general it has higher compression ratio comparing to GIF (and still lossless);

PNG supports images of most Graphics Mill for .NET pixel formats (indexed, grayscale, and RGB, including extended versions). Being web-oriented, it does not support CMYK images. Only single bitmap can be stored into single PNG file (i.e. it has no multiple frames support).

Examples

Also you can use PngWriter class instead of the Save(String, IEncoderOptions) method of the Bitmap. In particular it enables you to save the image asynchronously.

The PngWriter class usage is demonstrated below:

Dim bitmap As New Aurigma.GraphicsMill.Bitmap("c:\Mountain.jpg")

Dim writer As New Aurigma.GraphicsMill.Codecs.PngWriter("C:\Mountain.png")

Dim frame As New Aurigma.GraphicsMill.Codecs.PngFrame
frame.Interlaced = True
frame.SetBitmap(bitmap)

bitmap.Dispose()

writer.AddFrame(frame)

frame.Dispose()

writer.Dispose()

using (Aurigma.GraphicsMill.Bitmap bitmap = 
        new Aurigma.GraphicsMill.Bitmap(@"c:\Mountain.jpg"))
{
    using (Aurigma.GraphicsMill.Codecs.PngWriter writer = 
            new Aurigma.GraphicsMill.Codecs.PngWriter(@"C:\Mountain.png"))
    {
        using (Aurigma.GraphicsMill.Codecs.PngFrame frame = 
                   new Aurigma.GraphicsMill.Codecs.PngFrame())
        {
            frame.Interlaced = true;
            frame.SetBitmap(bitmap);
        
            writer.AddFrame(frame);                    
        }
    }        
}

This code sample converts the image into the indexed bitmap with 32 palette entries. After that it saves this bitmap into the PNG file.

Dim bitmap As New Aurigma.GraphicsMill.Bitmap("c:\Mountain.jpg")

bitmap.ColorManagement.PaletteEntryCount = 32
bitmap.ColorManagement.ConvertToIndexed(8, Aurigma.GraphicsMill.ColorPaletteType.Adaptive, _
    Nothing)

Dim writer As New Aurigma.GraphicsMill.Codecs.PngWriter("C:\Mountain.png")

Dim frame As New Aurigma.GraphicsMill.Codecs.PngFrame
frame.Interlaced = True
frame.SetBitmap(bitmap)

bitmap.Dispose()

writer.AddFrame(frame)

frame.Dispose()

writer.Dispose()

using (Aurigma.GraphicsMill.Bitmap bitmap = 
        new Aurigma.GraphicsMill.Bitmap(@"c:\Mountain.jpg"))
{
    bitmap.ColorManagement.PaletteEntryCount = 32;
    bitmap.ColorManagement.ConvertToIndexed(8, Aurigma.GraphicsMill.ColorPaletteType.Adaptive, 
        null);

    using (Aurigma.GraphicsMill.Codecs.PngWriter writer = 
            new Aurigma.GraphicsMill.Codecs.PngWriter(@"C:\Mountain.png"))
    {
        using (Aurigma.GraphicsMill.Codecs.PngFrame frame = 
                   new Aurigma.GraphicsMill.Codecs.PngFrame())
        {
            frame.Interlaced = true;
            frame.SetBitmap(bitmap);

            writer.AddFrame(frame);
        }
    }
}

Inheritance Hierarchy

Thread Safety

Object Model

Supported Pixel Formats

See Also

Reference

• PngWriter Members
• Aurigma.GraphicsMill.Codecs Namespace