Class AdvancedManipulations

java.lang.Object

AdvancedManipulations

public class AdvancedManipulations
extends java.lang.Object

Constructor Summary

Constructors

Constructor and Description
AdvancedManipulations()

Method Summary

Modifier and Type	Method and Description
static PixelPicture	adjustContrast(PixelPicture pic, double multiplier) Change the contrast of a picture.
static PixelPicture	blur(PixelPicture pic, int radius) Blur an image.
static PixelPicture	flood(PixelPicture pic, Pixel c, int x, int y) Challenge Problem (this problem is worth 0 points): Flood pixels of the same color with a different color.
static PixelPicture	reducePalette(PixelPicture pic, int numColors) Reduce a picture to its most common colors.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AdvancedManipulations

public AdvancedManipulations()

Method Detail

adjustContrast

public static PixelPicture adjustContrast(PixelPicture pic,
                                          double multiplier)

Change the contrast of a picture. Your job is to change the intensity of the colors in the picture. The simplest method of changing contrast is as follows: 1. Find the average color intensity of the picture. a) Sum the values of all the color components for each pixel. b) Divide the total by the number of pixels times the number of components (3). 2. Subtract the average color intensity from each color component of each pixel. This will make the average color intensity zero. 3. Scale the intensity of each pixel's color components by multiplying them by the "multiplier" parameter. Note that the multiplier is a double (a decimal value like 1.2 or 0.6) and color values are ints between 0 and 255. 4. Add the original average color intensity back to each component of each pixel. 5. Clip the color values so that all color component values are between 0 and 255. (See the clip method in the Pixel class.) Hint: You should use Math.round() before casting to an int for the average color intensity and for the scaled RGB values.

reducePalette

public static PixelPicture reducePalette(PixelPicture pic,
                                         int numColors)

Reduce a picture to its most common colors. You will need to make use of the ColorMap class to generate a map from Pixels of a certain color to the frequency with which identically-colored pixels appear in the image. Once you have generated your ColorMap, select your palette by retrieving the pixels whose color appears in the picture with the highest frequency. Then change each pixel in the picture to one with the closest matching color from your palette. Note that if there are two different colors that are the *same* minimal distance from the given color, your code should select the most frequently appearing one as the new color for the pixel. If both colors appear with the same frequency, your code should select the one that appears *first* in the output of the colormap's getSortedPixels. Algorithms like this are widely used in image compression. GIFs in particular compress the palette to no more than 255 colors. The variant we have implemented here is a weak one, since it only counts color frequency by exact match. Advanced palette reduction algorithms (known as "indexing" algorithms) calculate color regions and distribute the palette over the regions. For example, if our picture had a lot of shades of blue and a little bit of red, our algorithm would likely choose a palette of all blue colors. An advanced algorithm would recognize that blues look similar and distribute the palette so that it would be possible to display red as well.

Parameters:

pic - The Pixel for which the closest match should be found.

Returns:

The most closely matched Pixel from the palette.

blur

public static PixelPicture blur(PixelPicture pic,
                                int radius)

Blur an image. There are different blurring algorithms, but we'll use the simplest: box blur. Box blurring works by averaging the box-shaped neighborhood around a pixel. The size of the box is configurable by setting the radius, half the length of a side of the box. In the simplest case - a radius of 1 - blurring just takes the average around a pixel. For example, to blur around the pixel at (1,1) with radius 1, we take the average value of the pixels of its neighborhood: (0,0) though (2,2), including (1,1). NOTE: when blurring a pixel, make sure that you access the pixels in its neighborhood in the original image. You shouldn't use already "blurred" pixels to calculate the blur. Each Pixel is composed of 3 colors (red, green, and blue, or RGB) called components. Each component should be averaged separately. For a radius R, we set component c at location (x,y) according to the formula below: c = sum(c of each pixel within radius R) / ((2R + 1) * (2R + 1)) Logically, it makes sense that this would be the formula for the average. We sum the amount of each color in neighboring pixels and then divide by the number of pixels we considered in the neighborhood. Note that this equation disregards corner cases. When blurring (0,0) with radius 1, we only need to consider the top-left corner, (0,0) through (1,1) - we'll divide by 4 at the end, not 9. You'll have to be careful to only access bitmaps inside of their bounds. You can assume that you will not be given a radius less than 1. Note: In computing the average, you should be doing double division. Use Math.round() before casting to an int when computing the average. If you do not follow these specifications, the values you compute will not pass our tests.

Parameters:

pic - The picture to be blurred.

radius - The radius of the blurring box.

Returns:

A blurred version of the original picture.

flood

public static PixelPicture flood(PixelPicture pic,
                                 Pixel c,
                                 int x,
                                 int y)

Challenge Problem (this problem is worth 0 points): Flood pixels of the same color with a different color. The name is short for flood fill, which is the familiar "paint bucket" operation in graphics programs. In a paint program, the user clicks on a point in the image. Every neighboring, similarly-colored point is then "flooded" with the color the user selected. Suppose we want to flood color at (x,y). The simplest way to do flood fill is as follows: 1. Let target be the color at (x,y). 2. Create a set of points Q containing just the point (x,y). 3. Take the first point p out of Q. 4. Set the color at p to color. 5. For each of p's non-diagonal neighbors - up, down, left, and right - check to see if they have the same color as target. If they do, add them to Q. 6. If Q is empty, stop. Otherwise, go to 3. This is a naive algorithm that can be made significantly faster if you wish to try. For Q, you should use the provided IntQueue class. It works very much like the queues we implemented in OCaml.

Parameters:

pic - The original picture to be flooded.

c - The pixel the user "clicked" (representing the color that should be flooded).

x - The x-coordinate of the point on which the user "clicked."

y - The y-coordinate of the point on which the user "clicked."

Returns:

A new picture with the appropriate region flooded.