采样

1. 上采样 up sample

上采样可以用来进行图像放大，多采用内插方法，即在原有图像像素的基础上在像素点之间采用合适的插值算法插入新的元素。可以提升图片质量

Upsample VS Upscale:

upscaling is just enlarging pixels.  taking an image, say 1280x720 and stretching it to fit a screen with the resolution of 1920x1080.  Usually, the end result looks extremely blurry.（resize the picture）

upsampling calclulates extra pixels into the scaled image. basically "blurs edges of enlarged pixels so they wont look so sharp and blocky".

分类

Comparison gallery of image scaling algorithms - Wikipedia

a) 最近邻插值

replacing every pixel with multiple pixels of the same color

2. 下采样 down sample

缩小图像。对于一幅图像I尺寸为M*N，对其进行s倍下采样，即得到(M/s)*(N/s)尺寸的分辨率图像。

分类

a) Box sampling

consider the target pixel a box on the original image, and sample all pixels inside the box. This ensures that all input pixels contribute to the output.