Java实现图片比率缩放（java调整图片分辨率）

Java实现图片比率缩放（java调整图片分辨率）

本文实例为大家分享了java实现图片比率缩放的具体代码，供大家参考，具体内容如下

通过Thumbnails实现图片缩放

需要导入pom依赖，可以到中央仓库获取最小的工具包

net.coobird

thumbnailator

0.4.8

//读取图片

BufferedImage bufferedImage = ImageIO.read(new ByteArrayInputStream(out.toByteArray()));

ByteArrayOutputStream out2 = new ByteArrayOutputStream();

Thumbnails.of(bufferedImage).size(750,1344).outputFormat("png").toOutputStream(out2);//缩放图片

InitImage("缩放图", out2.toByteArray());//显示图片

java API实现图片缩放

调用方法

InitImage("自定义压缩图", zoomBySize(750,1334,bufferedImage,"png"));//调用方法

具体方法实现1

/**

*@description: 按比例对图片进行缩放. 检测图片是横图还是竖图

*@param : width 缩放后的宽

*@param : height 缩放后的高

*@param : img BufferedImage

*@param : ext 图片类型 如： jpg

*@author: YWR

*@return:

*@throws:

*@date: 2020/9/17 0:08

*/

public static byte[] zoomBySize(int width, int height, BufferedImage img, String ext) throws IOException {

//横向图

if (img.getWidth() >= img.getHeight()) {

double ratio = CalculateZoomRatio(width, img.getWidth());

//获取压缩对象

BufferedImagexcPZBu newbufferedImage = zoomByScale(ratio, img, ext);

//当图片大于图片压缩高时 再次缩放

if (newbufferedImage.getHeight() > height) {

ratio = CalculateZoomRatio(height, newbufferedImage.getHeight());

newbufferedImage = zoomByScale(ratio, img, ext);

}

ByteArrayOutputStream out = new ByteArrayOutputStream();

ImageIO.write(newbufferedImage, ext, out);

return out.toByteArray();

}

//纵向图

if (img.getWidth() < img.getHeight()) {

double ratio = CalculateZoomRatio(height, img.getHeight());

//获取压缩对象

BufferedImage newbufferedImage = zoomByScale(ratio, img, ext);

//当图片宽大于图片压缩宽时 再次缩放

if (newbufferedImage.getHeight() > height) {

ratio = CalculateZoomRatio(width, newbufferedImage.getWidth());

newbufferedImage = zoomByScale(ratio, img, ext);

}

ByteArrayOutputStream out = new ByteArrayOutputStream();

ImageIO.write(newbufferedImage, ext, out);

return out.toByteArray();

}

//以上都不符合时 强制缩放

Image _img = img.getScaledInstance(width, height, Image.SCALE_DEFAULT);

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics2D graphics = image.createGraphics();

graphics.drawImage(_img, 0, 0, null);

graphics.dispose();

ByteArrayOutputStream out = new ByteArrayOutputStream();

ImageIO.write(image, ext, out);

return out.toByteArray();

}

/**

*@description: 按比例对图片进行缩放.

*@param : scale 缩放比率

*@param : img BufferedImage

*@param : ext 图片类型

*@author: YWR

*@return:

*@throws:

*@date: 2020/9/17 0:07

*/

public static BufferedImage zoomByScale(double scale, BufferedImage img, String ext) throws IOException {

//获取缩放后的长和宽

int _width = (int) (scale * img.getWidth());

int _height = (int) (scale * img.getHeight());

//获取缩放后的Image对象

Image _img = img.getScaledInstance(_width, _height, Image.SCALE_DEFAULT);

//新建一个和Image对象相同大小的画布

BufferedImage image = new BufferedImage(_width, _height, BufferedImage.TYPE_INT_RGB);

//获取画笔

Graphics2D graphics = image.createGraphics();

//将Image对象画在画布上,最后一个参数,ImageObserver:接收有关 Image 信息通知的异步更新接口,没用到直接传空

graphics.drawImage(_img, 0, 0, null);

//释放资源

graphics.dispose();

return image;

}

/**

*@description: 缩放比率计算

*@param : divisor

*@param : dividend

*@author: YWR

*@return:

*@throws:

*@date: 2020/9/17 0:07

*/

private static double CalculateZoomRatio(int divisor, int dividend) {

return BigDecimal.valueOf(divisor).divide(BigDecimal.valueOf(dividend), 6, BigDecimal.ROUND_HALF_UP).doubleValue();

}

实现方法2

/**

*@description: 按比例对图片进行缩放. 检测图片是横图还是竖图

*@param : width 缩放后的宽

*@param : height 缩放后的高

*@param : img BufferedImage

*@param : ext 图片类型 如： jpg

*@author: YWR

*@return:

*@throws:

*@date: 2020/9/17 0:08

*/

public static byte[] zoomByScale(int width, int height, BufferedImage img, String ext) throws IOException {

//横向图

if (img.getWidth() >= img.getHeight()) {

double ratio = CalculateZoomRatio(width, img.getWidth());

//获取压缩对象

BufferedImage newbufferedImage = zoomByScale(ratio, img, ext);

//当图片大于图片压缩高时 再次缩放

if (newbufferedImage.getHeight() > height) {

ratio = CalculateZoomRatio(height, newbufferedImage.getHeight());

newbufferedImage = zoomByScale(ratio, img, ext);

}

ByteArrayOutputStream out = new ByteArrayOutputStream();

ImageIO.write(newbufferedImage, ext, out);

return out.toByteArray();

}

xcPZBu//纵向图

if (img.getWidth() < img.getHeight()) {

double ratio = CalculateZoomRatio(height, img.getHeight());

//获取压缩对象

BufferedImage newbufferedImage = zoomByScale(ratio, img, ext);

//当图片宽大于图片压缩宽时 再次缩放

if (newbufferedImage.getHeight() > height) {

ratio = CalculateZoomRatio(width, newbufferedImage.getWidth());

newbufferedImage = zoomByScale(ratio, img, ext);

}

ByteArrayOutputStream out = new ByteArrayOutputStream();

ImageIO.write(newbufferedImage, ext, out);

return out.toByteArray();

}

//以上都不符合时 强制缩放

Image _img = img.getScaledInstance(width, height, Image.SCALE_SMOOTH);

// 获取缩放比例

double wr=0,hr=0;

wr = width * 1.0 / img.getWidth();

hr = height * 1.0 / img.getHeight();

AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(wr, hr), null);

_img = ato.filter(img, null);

ByteArrayOutputStream out = new ByteArrayOutputStream();

ImageIO.write((BufferedImage) _img,ext,out);//写入缩减后的图片

return out.toByteArray();

}

/**

*@description: 按比例对图片进行缩放.

*@param : scale 缩放比率

*@param : img BufferedImage

*@param : ext 图片类型

*@author: YWR

*@return:

*@throws:

*@date: 2020/9/17 0:07

*/

public static BufferedImage zoomByScale(double scale, BufferedImage img, String ext) throws IOException {

//获取缩放后的长和宽

int _width = (int) (scale * img.getWidth());

int _height = (int) (scale * img.getHeight());

//设置缩放目标图片模板

Image _img = img.getScaledInstance(_width, _height, Image.SCALE_SMOOTH);

//缩放图片

AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(scale, scale), null);

_img = ato.filter(img, null);

return (BufferedImage) _img;

}

/**

*@description: 缩放比率计算

*@param : divisor

*@param : dividend

*@author: YWR

*@return:

*@throws:

*@date: 2020/9/17 0:07

*/

private static double CalculateZoomRatio(int dhttp://ivisor, int dividend) {

return BigDecimal.valueOf(divisor).divide(BigDecimal.valueOf(dividend), 6, BigDecimal.ROUND_HALF_UP).doubleValue();

}

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