Image File Formats PDF

# Image File Formats ## Common Image File Formats - **BMP** - bitmap image file, from Microsoft - **EPS** - Encapsulated Postscript - **GIF** - Graphics Interchange Format created by Compuserve in 1987 - **JPEG** - Created by the Joint Photographic Experts Group in 1992 - **PDF** - portable docume...

# Image File Formats ## Common Image File Formats - **BMP** - bitmap image file, from Microsoft - **EPS** - Encapsulated Postscript - **GIF** - Graphics Interchange Format created by Compuserve in 1987 - **JPEG** - Created by the Joint Photographic Experts Group in 1992 - **PDF** - portable document format - **PNG** - Portable Network Graphic - **PSD** - Photoshop Document - **RAW** - native raster digital camera file format - **SVG** - scalable vector graphics - **TIFF** - Tagged Image File Format - **TGA** - TARGA, from Truevison - **XCF** - the native GIMP format ## Key Concepts - **Raster vs Vector Graphics:** raster graphics use a grid of pixels to represent images. Vector graphics use geometric formulas. - **Lossy and lossless compression:** Lossy compression discards data to reduce the file size. Lossless compression reduces the file size without discarding any data. - **Colour spaces, bit depth and alpha channels:** The color space describes the range of colors that can be represented. Bit depth determine the number of colors that can be represented for each pixel. Alpha channels store pixel transparency information. ### Raster vs Vector Graphics Raster graphics are made up of pixels. Vector graphics are made of mathematical formulas. * **Raster:** Represented by individually colored grid of pixels. * **Vector:** Represented by mathematical descriptions (geometric formulas). ### Reducing File Size * **Lossy compression:** Discards information to reduce file size. Image quality may be affected. * **Non-lossy compression:** Retains all information while reducing file size. **Common compression methods:** - Discrete cosine transform (DCT) - Used for lossy compression - Run-length encoding (RLE) - Used for lossless compression ### Colour Channels * **RGB:** Red, Green, Blue * **CMYK:** Cyan, Magenta, Yellow, Black Most image formats store data in three color channels (RGB). Some formats support CMYK or a single black-and-white channel. ### Bit Depth & Alpha Channels * **Bit Depth:** refers to the number of bits used to represent a color component (red, green, blue) of a pixel. * **Alpha Channels:** Store transparency information. ### Image File Formats in Detail **JPEG** - Stores raster images in RGB or CMYK color spaces. - Uses DCT for lossy compression. - Does not support alpha channels. - Maximum 24-bit color. - Good for saving and sharing photographs but not ideal for print workflows. **PNG** - Stores raster images using non-lossy compression. - Can include an alpha channel. - Supports either 8-bit or 24-bit color but no CMYK option. - **PNG8:** 8-bit color - **PNG24:** 24-bit color - **PNG32:** 8 bpc RGBA, includes alpha channels. **GIF** - Raster-based. - Uses non-lossy compression. - Maximum 8-bit color (256 color palette). - Useful for web graphics, including animations. **TIFF** - Stores raster images with no compression, non-lossy compression, or lossy compression. - Supports RGB, CMYK, and B&W with 8, 16, or 32 bpc. - Includes an alpha channel. **PSD** - Adobe Photoshop’s native file format. - Primarily stores non-compressed raster images. - Can include vector text and other elements. - Supports RGB, CMYK, and B&W with 8, 16, or 32 bpc. - Layer-based with an alpha channel per layer. **RAW** - Native raster digital camera file format. - RGB color mode with 12, 14, or 16 bpc depending on the camera. - Direct binary data dump from the camera sensor. - Panasonic, Leica, and Casio cameras shoot .raw files. - Camera file extensions: .nef (Nikon), .cr2 (Canon), .arw (Sony) .dng, .dcr, and .nrw. ## Other Raster Image Formats * **JPEG, PNG, GIF, TIFF, PSD, and RAW:** The most common raster (bitmap) image formats. * **XCF:** The native GIMP format. * **BMP:** Bitmap image file, from Microsoft. * **TGA:** TARGA, from Truevision ## Vector Image Formats - **AI (Adobe Illustrator):** The dominant vector format, stores image elements mathematically. - **CDR (CorelDRAW):** Vector format commonly used for creating vector graphics. - **SVG:** Developed by the World Wide Web Consortium as an open standard. ## EPS & PDF - **EPS:** Encapsulated Postscript - **PDF:** Portable Document Format - Both are widely used for final delivery. - Largely vector-based but they allow raster images to be embedded.