How do you create a thumbnail image out of a JPEG in Java?

Question

Can someone please help with some code for creating a thumbnail for a JPEG in Java.

I\'m new at this, so a step by step explanation would be appreciated.

Answer 1

Maybe the simplest approach would be:

static public BufferedImage scaleImage(BufferedImage image, int max_width, int max_height) {
    int img_width = image.getWidth();
    int img_height = image.getHeight();

    float horizontal_ratio = 1;
    float vertical_ratio    = 1;


    if(img_height > max_height) {
        vertical_ratio = (float)max_height / (float)img_height;
    }
    if(img_width > max_width) {
        horizontal_ratio = (float)max_width / (float)img_width;
    }

    float scale_ratio = 1;

    if (vertical_ratio < horizontal_ratio) {
        scale_ratio = vertical_ratio;
    }
    else if (horizontal_ratio < vertical_ratio) {
        scale_ratio = horizontal_ratio;
    }

    int dest_width  = (int) (img_width * scale_ratio);
    int dest_height = (int) (img_height * scale_ratio);

    BufferedImage scaled = new BufferedImage(dest_width, dest_height, image.getType());
    Graphics graphics = scaled.getGraphics();
    graphics.drawImage(image, 0, 0, dest_width, dest_height, null);
    graphics.dispose();

    return scaled;

}