Bitmap/Read a PPM file: Difference between revisions
→{{header|Java}}
Line 1,812:
<syntaxhighlight lang="java">
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.imageio.ImageIO;
public class ReadPPMFile {
public static void main(String[] aArgs) throws IOException {
String filePath = "C:/Users/psnow/Desktop/output.ppm";
reader = new BufferedInputStream( new FileInputStream(filePath) );
final char header1 = (char) reader.read();
final char header2 = (char) reader.read();
final char header3 = (char) reader.read();
if ( header1 != 'P' || header2 != '6' || header3 != END_OF_LINE) {
reader.close();
throw new IllegalArgumentException("Not a valid P6 PPM file");
}
final int width = processCharacters(SPACE_CHARACTER);
final int height = processCharacters(END_OF_LINE);
final int maxColorValue = processCharacters(END_OF_LINE);
if ( maxColorValue < 0 || maxColorValue > 255 ) {
reader.close();
throw new IllegalArgumentException("Maximum color value is outside the range 0..255");
}
// Remove any comments before reading data
reader.mark(1);
while ( reader.read() == START_OF_COMMENT) {
while ( reader.read() != END_OF_LINE );
reader.mark(1);
}
reader.reset();
// Read data
BasicBitmapStorage bitmap = new BasicBitmapStorage(width, height);
byte[] buffer = new byte[width * 3];
for ( int y = 0; y < height; y++ ) {
reader.read(buffer, 0, buffer.length);
for ( int x = 0; x < width; x++ ) {
Color color = new Color(Byte.toUnsignedInt(buffer[x * 3]),
Byte.toUnsignedInt(buffer[x * 3 + 1]),
Byte.toUnsignedInt(buffer[x * 3 + 2]));
bitmap.setPixel(x, y, color);
}
}
reader.close();
// Convert to gray scale and save to a file
bitmap.convertToGrayscale();
File grayFile = new File("C:/Users/psnow/Desktop/outputGray.jpg");
ImageIO.write((RenderedImage) bitmap.getImage(), "jpg", grayFile);
}
private static int processCharacters(char aChar) throws IOException {
StringBuilder characters = new StringBuilder();
char ch;
while ( ( ch = (char) reader.read() ) != aChar ) {
if ( ch == START_OF_COMMENT ) {
while ( reader.read() != END_OF_LINE );
continue;
}
characters.append(ch);
}
return Integer.valueOf(characters.toString());
}
private static BufferedInputStream reader;
private static final char START_OF_COMMENT = '#';
private static final char SPACE_CHARACTER = ' ';
private static final char END_OF_LINE = '\n';
}
final class BasicBitmapStorage {
public BasicBitmapStorage(int aWidth, int aHeight) {
image = new BufferedImage(aWidth, aHeight, BufferedImage.TYPE_INT_RGB);
}
public void fill(Color aColor) {
Graphics graphics = image.getGraphics();
graphics.setColor(aColor);
graphics.fillRect(0, 0, image.getWidth(), image.getHeight());
}
public Color getPixel(int aX, int aY) {
return new Color(image.getRGB(aX, aY));
}
public void setPixel(int aX, int aY, Color aColor) {
image.setRGB(aX, aY, aColor.getRGB());
}
public Image getImage() {
return image;
}
public void convertToGrayscale() {
for ( int y = 0; y < image.getHeight(); y++ ) {
for ( int x = 0; x < image.getWidth(); x++ ) {
int color = image.getRGB(x, y);
int alpha = ( color >> 24 ) & 255;
int red = ( color >> 16 ) & 255;
int green = ( color >> 8 ) & 255;
int blue = color & 255;
final int luminance = (int) ( 0.2126 * red + 0.7152 * green + 0.0722 * blue );
alpha = alpha << 24;
red = luminance << 16;
green = luminance << 8;
blue = luminance;
color = alpha + red + green + blue;
image.setRGB(x, y, color);
}
}
}
private final BufferedImage image;
}
</syntaxhighlight>
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