How to use the command 'convert' (with examples)

The ‘convert’ command is an image conversion tool that is part of ImageMagick. It allows you to perform various operations on images, such as converting file formats, resizing, appending images, creating animations, and more.

Use case 1: Convert an image from JPG to PNG

Code:

convert path/to/input_image.jpg path/to/output_image.png

Motivation: This use case is useful when you have an image in JPG format and you need to convert it to PNG. PNG is a lossless file format that supports transparency, making it ideal for certain use cases, such as web design.

Explanation:

• path/to/input_image.jpg is the path to the input image in JPG format.
• path/to/output_image.png is the path where you want to save the converted image in PNG format.

Example output: The image at path/to/input_image.jpg will be converted to PNG format and saved at path/to/output_image.png.

Use case 2: Scale an image to 50% of its original size

Code:

convert path/to/input_image.png -resize 50% path/to/output_image.png

Motivation: Sometimes, you may need to resize an image to fit a specific requirement, such as reducing its dimensions to save storage or optimize its display on a webpage.

Explanation:

• path/to/input_image.png is the path to the input image.
• -resize 50% specifies that the image should be scaled to 50% of its original size.
• path/to/output_image.png is the path where you want to save the resized image.

Example output: The image at path/to/input_image.png will be scaled to 50% of its original size and saved at path/to/output_image.png.

Use case 3: Scale an image keeping the original aspect ratio to a maximum dimension of 640x480

Code:

convert path/to/input_image.png -resize 640x480 path/to/output_image.png

Motivation: In certain cases, you may want to resize an image while ensuring it maintains its original aspect ratio to avoid distortion or loss of image quality.

Explanation:

• path/to/input_image.png is the path to the input image.
• -resize 640x480 specifies that the image should be scaled to a maximum dimension of 640x480. The aspect ratio of the original image will be maintained.

Example output: The image at path/to/input_image.png will be scaled to fit within a maximum dimension of 640x480 and saved at path/to/output_image.png.

Use case 4: Horizontally append images

Code:

convert path/to/image1.png path/to/image2.png ... +append path/to/output_image.png

Motivation: When you have multiple images and you want to concatenate or combine them horizontally, this use case becomes handy.

Explanation:

• path/to/image1.png path/to/image2.png ... are the paths to the input images that you want to append horizontally.
• +append specifies the operation to horizontally append the images.
• path/to/output_image.png is the path where you want to save the resulting image.

Example output: The images at path/to/image1.png and path/to/image2.png will be horizontally appended, and the resulting image will be saved at path/to/output_image.png.

Use case 5: Vertically append images

Code:

convert path/to/image1.png path/to/image2.png ... -append path/to/output_image.png

Motivation: Similar to the previous use case, this is useful when you want to combine multiple images, but in this case, vertically.

Explanation:

• path/to/image1.png path/to/image2.png ... are the paths to the input images that you want to append vertically.
• -append specifies the operation to vertically append the images.
• path/to/output_image.png is the path where you want to save the resulting image.

Example output: The images at path/to/image1.png and path/to/image2.png will be vertically appended, and the resulting image will be saved at path/to/output_image.png.

Use case 6: Create a GIF from a series of images with 100ms delay between them

Code:

convert path/to/image1.png path/to/image2.png ... -delay 10 path/to/animation.gif

Motivation: Creating animations or slideshows using a series of images is a common task. This use case allows you to convert a set of images into a GIF with a specified delay between frames.

Explanation:

• path/to/image1.png path/to/image2.png ... are the paths to the input images that you want to include in the animation.
• -delay 10 specifies the delay between frames in the GIF. In this case, the delay is set to 100ms.
• path/to/animation.gif is the path where you want to save the resulting GIF.

Example output: The images at path/to/image1.png, path/to/image2.png, etc., will be combined into an animation with a 100ms delay between frames, and the resulting GIF will be saved at path/to/animation.gif.

Use case 7: Create an image with nothing but a solid red background

Code:

convert -size 800x600 "xc:#ff0000" path/to/image.png

Motivation: Sometimes, you may need a simple image with a solid color background for various purposes, such as creating placeholders or background images.

Explanation:

• -size 800x600 specifies the dimensions of the output image. In this case, the image will be 800 pixels wide and 600 pixels high.
• "xc:#ff0000" is a string that represents the solid red color for the background. You can specify any other color using different hexadecimal values.
• path/to/image.png is the path where you want to save the resulting image.

Example output: A new image with a solid red background, measuring 800x600 pixels, will be created and saved at path/to/image.png.

Use case 8: Create a favicon from several images of different sizes

Code:

convert path/to/image1.png path/to/image2.png ... path/to/favicon.ico

Motivation: Favicon is a small icon that represents a website or webpage, typically displayed in the browser’s address bar or next to the page title. This use case allows you to create a favicon by combining multiple images of different sizes.

Explanation:

• path/to/image1.png path/to/image2.png ... are the paths to the input images that you want to use for creating the favicon. The images can be of different sizes.
• path/to/favicon.ico is the path where you want to save the resulting favicon. The file format for favicon is typically ICO.

Example output: The images at path/to/image1.png, path/to/image2.png, etc., will be combined to create a favicon file at path/to/favicon.ico. The resulting file can then be used as a favicon for your website or webpage.

Conclusion:

The ‘convert’ command in ImageMagick provides a versatile set of features for manipulating and transforming images. With the examples provided, you can now perform image conversions, resize images, append images horizontally or vertically, create animations, generate images with solid backgrounds, and even create favicons. Whether you are a web designer, developer, or working with image processing, the ‘convert’ command can help you accomplish various image-related tasks efficiently.