Codec.Picture.Png

Module used for loading & writing 'Portable Network Graphics' (PNG) files.

A high level API is provided. It loads and saves images for you while hiding all the details about PNG chunks.

Basic functions for PNG handling are decodePng, encodePng and encodePalettedPng. Convenience functions are provided for direct file handling and using DynamicImages.

The loader has been validated against the pngsuite (http:/www.libpng.orgpubpngpngsuite.html)

High level functions

class PngSavable a where

Encode an image into a png if possible.

Minimal complete definition

encodePngWithMetadata

Methods

encodePng :: Image a -> ByteString

Transform an image into a png encoded bytestring, ready to be written as a file.

encodePngWithMetadata :: Metadatas -> Image a -> ByteString

Encode a png using some metadatas. The following metadata keys will be stored in a tEXt field :

• Title
• Description
• Author
• Copyright
• Software
• Comment
• Disclaimer
• Source
• Warning
• Unknown using the key present in the constructor.

the followings metadata will bes tored in the gAMA chunk.

• Gamma

The followings metadata will be stored in a pHYs chunk

• DpiX
• DpiY

Instances

PngSavable PixelRGBA16

Methods

encodePng :: Image PixelRGBA16 -> ByteString

encodePngWithMetadata :: Metadatas -> Image PixelRGBA16 -> ByteString

PngSavable PixelRGBA8

Methods

encodePng :: Image PixelRGBA8 -> ByteString

encodePngWithMetadata :: Metadatas -> Image PixelRGBA8 -> ByteString

PngSavable PixelRGB16

Methods

encodePng :: Image PixelRGB16 -> ByteString

encodePngWithMetadata :: Metadatas -> Image PixelRGB16 -> ByteString

PngSavable PixelRGB8

Methods

encodePng :: Image PixelRGB8 -> ByteString

encodePngWithMetadata :: Metadatas -> Image PixelRGB8 -> ByteString

PngSavable PixelYA16

Methods

encodePng :: Image PixelYA16 -> ByteString

encodePngWithMetadata :: Metadatas -> Image PixelYA16 -> ByteString

PngSavable PixelYA8

Methods

encodePng :: Image PixelYA8 -> ByteString

encodePngWithMetadata :: Metadatas -> Image PixelYA8 -> ByteString

PngSavable Pixel16

Methods

encodePng :: Image Pixel16 -> ByteString

encodePngWithMetadata :: Metadatas -> Image Pixel16 -> ByteString

PngSavable Pixel8

Methods

encodePng :: Image Pixel8 -> ByteString

encodePngWithMetadata :: Metadatas -> Image Pixel8 -> ByteString

class PngPaletteSaveable a where

Encode a paletted image into a png if possible.

Minimal complete definition

encodePalettedPngWithMetadata

Methods

encodePalettedPng :: Image a -> Image Pixel8 -> Either String ByteString

Encode a paletted image as a color indexed 8-bit PNG. the palette must have between 1 and 256 values in it. Accepts PixelRGB8 and PixelRGBA8 as palette pixel type

encodePalettedPngWithMetadata :: Metadatas -> Image a -> Image Pixel8 -> Either String ByteString

Equivalent to encodePalettedPng but allow writing of metadatas. See encodePngWithMetadata for the details of encoded metadatas Accepts PixelRGB8 and PixelRGBA8 as palette pixel type

Instances

PngPaletteSaveable PixelRGBA8

Methods

encodePalettedPng :: Image PixelRGBA8 -> Image Pixel8 -> Either String ByteString

encodePalettedPngWithMetadata :: Metadatas -> Image PixelRGBA8 -> Image Pixel8 -> Either String ByteString

PngPaletteSaveable PixelRGB8

Methods

encodePalettedPng :: Image PixelRGB8 -> Image Pixel8 -> Either String ByteString

encodePalettedPngWithMetadata :: Metadatas -> Image PixelRGB8 -> Image Pixel8 -> Either String ByteString

decodePng :: ByteString -> Either String DynamicImage

Transform a raw png image to an image, without modifying the underlying pixel type. If the image is greyscale and < 8 bits, a transformation to RGBA8 is performed. This should change in the future. The resulting image let you manage the pixel types.

This function can output the following images:

• ImageY8
• ImageY16
• ImageYA8
• ImageYA16
• ImageRGB8
• ImageRGB16
• ImageRGBA8
• ImageRGBA16

decodePngWithMetadata :: ByteString -> Either String (DynamicImage, Metadatas)

Decode a PNG file with, possibly, separated palette.

decodePngWithPaletteAndMetadata :: ByteString -> Either String (PalettedImage, Metadatas)

Same as decodePng but also extract meta datas present in the files.

writePng :: PngSavable pixel => FilePath -> Image pixel -> IO ()

Helper function to directly write an image as a png on disk.

encodeDynamicPng :: DynamicImage -> Either String ByteString

Encode a dynamic image in PNG if possible, supported images are:

• ImageY8
• ImageY16
• ImageYA8
• ImageYA16
• ImageRGB8
• ImageRGB16
• ImageRGBA8
• ImageRGBA16

encodePalettedPng :: PngPaletteSaveable a => Image a -> Image Pixel8 -> Either String ByteString

Encode a paletted image as a color indexed 8-bit PNG. the palette must have between 1 and 256 values in it. Accepts PixelRGB8 and PixelRGBA8 as palette pixel type

encodePalettedPngWithMetadata :: PngPaletteSaveable a => Metadatas -> Image a -> Image Pixel8 -> Either String ByteString

Equivalent to encodePalettedPng but allow writing of metadatas. See encodePngWithMetadata for the details of encoded metadatas Accepts PixelRGB8 and PixelRGBA8 as palette pixel type

writeDynamicPng :: FilePath -> DynamicImage -> IO (Either String Bool)

Write a dynamic image in a .png image file if possible. The same restriction as encodeDynamicPng apply.