所以你刚刚从你的新佳能(Canon)或尼康(Nikon)相机上下载了一些照片？好吧(Well)，准备好一些高分辨率的大图片！您说的是 20+ 百万像素和极高的分辨率！价格总是在下降，质量总是在上升。对于大多数人来说，这太过分了。
此外，有时很难在大小、存储和与他人共享图片方面管理所有额外质量。当然，如果您使用Google Photos之类的服务，您可以以原始分辨率上传所有照片，并以这种方式与他人分享相册，而无需缩小图像。
但是，有时您需要按比例缩小图像，例如将其放在网站上或将其插入Word文档或PowerPoint演示文稿中。以全分辨率添加它不会带来额外的好处，只会减慢您的网页速度或使您的Word或PowerPoint文档变得巨大。
在 Windows 中缩小图像
对于Windows，我喜欢使用Paint。如果您不需要调整数百张照片的大小，那么Paint就可以了。打开带有照片的画图(Paint)，您将在功能区中看到调整大小(Resize)按钮。
单击(Click)它，您可以按百分比或像素调整大小。您还可以自动保持或不保持纵横比。
如果你想要一个更高级的程序来调整图像大小，你可以使用一个叫做Gimp的程序。它是免费的，并且有一些用于缩放图像的好工具。你可以在这里下载：
https://www.gimp.org/
安装后，打开图像，然后单击图像(Image)和缩放图像( Scale Image)。
请注意，在Gimp 2.8中，您可以将所有窗口合并到一个窗口中，而不是所有的东西都漂浮在各处。您可以通过转到Windows并单击Single Window Mode来做到这一点。
如果发现这种方式更容易使用。无论如何(Anyway)，一旦出现缩放图像对话框，您将看到几个选项：
您可以通过调整宽度和高度来直接更改图像大小。这是缩放图像的最常用方法。您还可以调整分辨率，这将允许您在线查看原始尺寸的图像，但会降低打印质量。大多数屏幕可以显示的空间分辨率是 72 或 100（PPI或像素/英寸）。这意味着您可以将分辨率降低到 72 或 100 ppi，而计算机屏幕上的图像不会有任何明显差异，并且会显着减小图像尺寸。
请注意，几年前计算机屏幕最常见的分辨率是 1024×768。即使你采用更高的分辨率，比如 1600×1200，你仍然可以将这些非常大的图像的宽度缩小到 1000 像素以下，但它仍然会占据整个屏幕。
另请注意，更改宽度或高度时，默认情况下将保持纵横比。如果您单击右侧的小链，它将“取消链接”，然后您可以独立更改宽度或高度，这将拉伸您的图像。如果您不希望它拉伸，则必须裁剪图像，这有点像缩放，但不一样，因为您要删除图像的一部分。缩放时，始终保持整个图像。
最后，您可以选择确定缩放质量的插值方法。(Interpolation)默认情况下，它设置为Cubic。以下是不同选项之间的区别：
无(None)– 像素的颜色由图片中最近的邻居决定。这是最快的方法，但会导致图像粗糙。
线性(Linear)- 像素的颜色由图片中四个最近像素的平均颜色决定。这使图片看起来比前一个选项更平滑。
立方(Cubic)- 像素的颜色由图片中最接近的八个像素的平均颜色决定。几乎相同，但同样，按比例缩小的图像更平滑，此选项将提供最佳结果。
Sinc (Lanczos3) - 此方法使用称为Sinc的数学公式并进行高质量插值。
这就是在Windows中缩放图像的内容。
在 OS X 中按比例缩小图像
如果您想在OS X中缩放图像，您无需安装任何额外的软件。您可以使用内置的预览(Preview)程序。打开图像时，单击工具(Tools)，然后单击调整大小(Adjust Size)。
这将打开大小调整对话框，您在其中几乎可以使用与我在GIMP中展示的选项相同的选项：
您可以根据需要调整宽度和高度并更改分辨率。它还告诉您在实际进行更改之前生成的大小是多少，这很好。
在 iOS 中缩小图像
如果您在 iPhone 或 iPad 上工作，并且想要快速将图像缩小到特定尺寸，您可以尝试一个名为Image Size的免费程序。它似乎为大多数人完成了工作。
值得注意的是，iOS中的默认照片应用程序现在可以进行一些简单的缩放，但只能使用预设选项。(Photos)点击照片，然后点击右上角的编辑(Edit)。屏幕底部出现几个小图标。继续并点击最左侧的旋转/裁剪图标。
接下来，您将看到一个新图标出现在最右侧稍高的位置。此图标用于更改照片的尺寸。
现在您可以从一组预设比率中进行选择。这包括正方形、2:3、3:5、3:4 等。
对于大多数人来说，如果他们只想发布到Instagram等就足够了，所以你真的不需要应用程序。
在 Android 中缩小图像
最后，我们不要忘记那些Android用户。Photo & Picture Resizer是一款免费的应用程序，可让您调整图像的大小和质量。
就是这样！希望(Hopefully)这涵盖了人们用来缩放图像的最常见的操作系统和平台。有任何问题或意见吗？把它们贴在这里。享受！
Scale Down an Image in Windows, Mac, iOS, and Android
So you just dоwnloaded some piсtures from your new fanсy Canon or Nikon camera? Well, get rеady for some huge pictures with lots of resolution! You’re tаlking aboυt 20+ megapixelѕ and extremely high resolutions! The prices are alwaуs coming down and the quality is always going up. For most people, it’s overkill.
Additionally, it’s sometimes hard to manage all that extra quality in terms of size, storing and sharing your pictures with others. Of course, if you use a service like Google Photos, you can upload all your photos in their native resolution and share albums with others that way, bypassing the need to scale down your images.
However, there are times when you will need to scale an image down, such as putting it up on a website or inserting it into a Word document or PowerPoint presentation. Adding it at full resolution will provide no additional benefit and will only slow down your webpage or make your Word or PowerPoint document huge.
Scale Down Image in Windows
For Windows, I like to use Paint. If you don’t need to resize hundreds of photos, then Paint works just fine. Open Paint with the photo and you’ll see a Resize button in the ribbon.
Click on that and you can resize by percentage or by pixels. You can also automatically maintain the aspect ratio or not.
If you want a little fancier program for resizing images, you can use a program called the Gimp. It’s free and it has some nice tools for scaling images. You can download it here:
https://www.gimp.org/
Once you have it installed, open your image and then click on Image and Scale Image.
Note that in Gimp 2.8, you can combine all the windows into a single window instead of everything floating around all over the place. You can do that by going to Windows and clicking on Single Window Mode.
If find this way easier to work with. Anyway, once the scale image dialog appears, you’ll see a couple of options:
You can change the image size directly by adjusting the width and the height. This is the most common way to scale an image. You can also adjust the resolution, which will allow you to view the image in its original size online, but reduce the print quality. The spatial resolution most screens can show is 72 or 100 (PPI or pixels/in). This means you can reduce the resolution to 72 or 100 ppi without any noticeable difference in the image on a computer screen and it will reduce your image size significantly.
Note that the most common resolution for computer screens a couple of years ago was 1024×768. Even if you take a higher resolution like 1600×1200, you can still reduce the width of these really huge images under 1000 pixels and still it will take up the entire screen.
Also note that when changing the width or height, the aspect ratio will be maintained by default. If you click on the little chain to the right, it will “unlink” and you can then change the width or the height independently, which will stretch your image. If you don’t want it to stretch, then you have to crop the image, which is kind of like scaling, but not the same since you’re removing parts of the image. When scaling, the whole image is always maintained.
Lastly, you can choose the Interpolation method, which determines the quality of the scaling. By default, it’s set to Cubic. Here is the difference between the different options:
None – The color of a pixel is determined by its closest neighbor in the picture. It’s the fastest method, but can result in a coarse image.
Linear – The color of a pixel is determined by the average color of the four closest pixels in the picture. This makes the picture look smoother than the previous option.
Cubic – The color of a pixel is determined by the average color of the eight closest pixels in the picture. Pretty much the same, but again, the scaled down image is smoother and this option will give the best result.
Sinc (Lanczos3) – This method uses a mathematical formula called Sinc and does a high quality interpolation.
That’s about it for scaling images in Windows.
Scale Down Image in OS X
If you want to scale an image in OS X, you don’t have to install any additional software. You can use the built-in Preview program. When you open your image, click on Tools and then Adjust Size.
This will bring up the size adjust dialog where you pretty much have the same options as I showed you in GIMP:
You can adjust the width and height and change the resolution also if you like. It also tells you what the resulting size will be before you actually make the change, which is nice.
Scale Down Image in iOS
If you are working from your iPhone or iPad and want a quick way to scale down an image to a specific size, you can try out a free program called Image Size. It seems to get the job done for most people.
It’s worth noting that the default Photos app in iOS can now do some simple scaling, but only with preset options. Tap on the photo and then tap on Edit at the top right. A few small icons appear at the bottom of the screen. Go ahead and tap on the rotate/crop icon at the far left.
Next, you will see a new icon appear a little higher up at the far right. This icon is for changing the dimensions of the photo.
Now you’ll get to choose from a set of preset ratios. This includes square, 2:3, 3:5, 3:4, etc.
For most people, this will be enough if they just want to post to Instagram, etc., so you really don’t need an app.
Scale Down Image in Android
Lastly, let’s not forget about those Android users. Photo & Picture Resizer is a free app that lets you adjust the size and quality of an image.
That’s about it! Hopefully, that covers the most common operating systems and platforms that people will use to scale images. Any questions or comments? Post them here. Enjoy!
