Photo Editing with GIMP

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Photo Editing with GIMP. Workshop Presenter: George E. Brooks Cumberland County Schools South View High School Workshop objectives. GIMP Downloads Grayscale Desaturate RGB Color Curves HSV LAB CMYK. Automatic Color-Stretching Auto Modes Map Filters - PowerPoint PPT Presentation


Photo Editing with GIMP

Auto EqualizeEqualize applied to flower

GIMP DownloadsSoftware Version GIMP for various operating systems Website address for downloading: XPSP3 or higher:Windows Operating System MACs

GrayscaleHere is what I get if I use the standard mode change to grayscale from RGB.Duplicate the original image (Ctrl+D) and right-click on the copy. Select Image -> Mode -> Grayscale

DesaturateBy using the Desaturate command, you can convert all of the colors on the active layer to corresponding shades of gray. This differs from converting the image to grayscale in two respects. First, it only operates on the active layer and second, the colors on the layer are still RGB values with three components. This means that you can paint on the layer, or individual parts of it, using color at a later timeGrayscaleYou can use the Grayscale command to convert your image to grayscale with 256 levels of gray, from 0 (black) to 255 (white).Before Grayscale

After Grayscale

DesaturateSelect Image -> Colors -> Desaturate.

Before Desaturate

Auto ModesEqualizeWhite BalanceColor EnhanceNormalizeStretch ContrastStretch HSV

MAP FiltersMap filters use an object named map to modify an image: you map the image to the object.Types:AlienColor ExchangeGradientPaletteRotate ColorsSample Colorize

ColorifyThis filter renders a greyscale image like it is seen through a colored glass.For every pixel, the filter computes a weighted average value of the RGB channels (this is equivalent to desaturation the image based on luminosity). The resulted color is the product of this average value and the colorify color. Hence, this filter works only on images in RGB mode.

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Work CitedPeck, Akkana. Beginning GIMP: From Novice to Professional. Apress, 2006. Books. 07 July 2007. .Beginning GIMP: From Novice to Professional, Second Edition. 2nd. Apress, 2008. Book. 07 July 2012.Simoni., Jernej. GIMP for Windows. 01 January 2013. Web Site. 07 July 2013.Simone, Lisa. GIMP on OS X. 13 January 2013. Web Site. 07 January 2013.Team, GIMP Development. GIMP Tutorials'. 01 January 2013. Web Site. 07 07 2013.Team, The GIMP Documentation. GNU Image Manipulation Program User Manual. 01 January 2012. Web Site. 07 July 2013.Hue, Saturation and Value (HSV)This option decomposes image into three greyscale layers, one for Hue, one for Saturation and another for Value. Although Hue is greyscale, it does represent hues. In color circle, white and black are starting and arrival points and are superimposed. They represent Red color at top of circle. Grey intermediate levels are corresponding to intermediate hues on circle: dark grey to orange, mid grey to green and light grey to magenta. Saturation and Value: White is maximum Saturation (pure color) and maximum Value (very bright). Black is minimum Saturation (white) and minimum Value (black).

Before Decompose HSV

Decompose HSVSelect Image -> Colors -> Hue-Saturation

LABThis option decomposes image into three greyscaled layers, layer L for Luminance, layer A for colors between green and red, layer B for colors between blue and yellow. The LAB Decomposing is a color model of the Luminance-Color family. A channel is used for the Luminosity while two other channels are used for the Colors. The LAB color model is used by Photoshop.

Before Decompose LAB

Decompose LABThe Lightness component is a very interesting one because it contains all of the luminance information.

After LAB

CMYKThe CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black). Though it varies by print house, press operator, press manufacturer, and press run, ink is typically applied in the order of the abbreviation.

Before CMYK

Decompose CMYKSelect Image -> Colors -> Components, Decompose

Make sure to switch to Color Model to CMYK

After CMKY Decompose

Automatic Color-StretchingGIMPhas several automatic commands for stretching the columns of the histogram for the color channels of the active layer. By pushing bright pixels to the right and dark pixels to the left, they make bright pixels brighter and dark pixels darker, which enhances the contrast in the layer.Some of the commands stretch the three color channels equally, so that the hues are not changed. Other commands stretch each of the color channels separately, which changes the hues.

AlienAlien-This filter renders very modified colors by applying trigonometric functions. Alien Map can work on images having RGB and HSV color models.

Color ExchangeColor ExchangeThis filter replaces a color with another one.

GradientGradientThis filter uses the current gradient, as shown in the Brush/Pattern/Gradient area of the Toolbox, to recolor the active layer or selection of the image to which the filter is applied

PalettePaletteThis plug-in recolors the image using colors from the active palette that you choose inDialogsPalettes.

Rotate ColorsRotate ColorsColormap Rotation lets you exchange one color range to another range.

Sample ColorizeSample ColorizeThis filter allows you to colorize old black-and-white images by mapping a color source image or a gradient against it.

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