Add zoom option

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## [Unreleased]
 ### Added
 - (pro) Add `video_meta` to the `/info` response.
+- Add [zoom](https://docs.imgproxy.net/generating_the_url?id=zoom) processing option.
 - Add 1/2/4-bit BMP support.
 
 ### Change

docs/generating_the_url.md

@@ -121,6 +121,24 @@ Defines the minimum height of the resulting image.
 
 Default: `0`
 
+### Zoom
+
+```
+zoom:%zoom_x_y
+z:%zoom_x_y
+
+zoom:%zoom_x %zoom_y
+z:%zoom_x %zoom_y
+```
+
+When set, imgproxy will multiply the image dimensions according to these factors. The values must be greater than 0.
+
+Can be combined with `width` and `height` options. In this case, imgproxy calculates scale factors for the provided size and then multiplies it with the provided zoom factors.
+
+**📝Note:** Unlike [dpr](#dpr), `zoom` doesn't set `Content-DPR` header in the response.
+
+Default: `1`
+
 ### Dpr
 
 ```
@@ -129,6 +147,8 @@ dpr:%dpr
 
 When set, imgproxy will multiply the image dimensions according to this factor for HiDPI (Retina) devices. The value must be greater than 0.
 
+**📝Note:** `dpr` also sets `Content-DPR` header in the response so the browser can render the image correctly.
+
 Default: `1`
 
 ### Enlarge

options/processing_options.go

@@ -65,6 +65,8 @@ type ProcessingOptions struct {
 	Height            int
 	MinWidth          int
 	MinHeight         int
+	ZoomWidth         float64
+	ZoomHeight        float64
 	Dpr               float64
 	Gravity           GravityOptions
 	Enlarge           bool
@@ -115,6 +117,8 @@ func NewProcessingOptions() *ProcessingOptions {
 			ResizingType:      ResizeFit,
 			Width:             0,
 			Height:            0,
+			ZoomWidth:         1,
+			ZoomHeight:        1,
 			Gravity:           GravityOptions{Type: GravityCenter},
 			Enlarge:           false,
 			Extend:            ExtendOptions{Enabled: false, Gravity: GravityOptions{Type: GravityCenter}},
@@ -375,6 +379,31 @@ func applyResizeOption(po *ProcessingOptions, args []string) error {
 	return nil
 }
 
+func applyZoomOption(po *ProcessingOptions, args []string) error {
+	nArgs := len(args)
+
+	if nArgs > 2 {
+		return fmt.Errorf("Invalid zoom arguments: %v", args)
+	}
+
+	if z, err := strconv.ParseFloat(args[0], 64); err == nil && z > 0 {
+		po.ZoomWidth = z
+		po.ZoomHeight = z
+	} else {
+		return fmt.Errorf("Invalid zoom value: %s", args[0])
+	}
+
+	if nArgs > 1 {
+		if z, err := strconv.ParseFloat(args[1], 64); err == nil && z > 0 {
+			po.ZoomHeight = z
+		} else {
+			return fmt.Errorf("Invalid zoom value: %s", args[0])
+		}
+	}
+
+	return nil
+}
+
 func applyDprOption(po *ProcessingOptions, args []string) error {
 	if len(args) > 1 {
 		return fmt.Errorf("Invalid dpr arguments: %v", args)
@@ -822,6 +851,8 @@ func applyURLOption(po *ProcessingOptions, name string, args []string) error {
 		return applyMinWidthOption(po, args)
 	case "min-height", "mh":
 		return applyMinHeightOption(po, args)
+	case "zoom", "z":
+		return applyZoomOption(po, args)
 	case "dpr":
 		return applyDprOption(po, args)
 	case "enlarge", "el":

processing/crop.go

@@ -53,8 +53,7 @@ func crop(pctx *pipelineContext, img *vips.Image, po *options.ProcessingOptions,
 
 func cropToResult(pctx *pipelineContext, img *vips.Image, po *options.ProcessingOptions, imgdata *imagedata.ImageData) error {
 	// Crop image to the result size
-	resultWidth := imath.Scale(po.Width, po.Dpr)
-	resultHeight := imath.Scale(po.Height, po.Dpr)
+	resultWidth, resultHeight := resultSize(po)
 
 	if po.ResizingType == options.ResizeFillDown {
 		if resultWidth > img.Width() {

processing/extend.go

@@ -2,14 +2,12 @@ package processing
 
 import (
 	"github.com/imgproxy/imgproxy/v3/imagedata"
-	"github.com/imgproxy/imgproxy/v3/imath"
 	"github.com/imgproxy/imgproxy/v3/options"
 	"github.com/imgproxy/imgproxy/v3/vips"
 )
 
 func extend(pctx *pipelineContext, img *vips.Image, po *options.ProcessingOptions, imgdata *imagedata.ImageData) error {
-	resultWidth := imath.Scale(po.Width, po.Dpr)
-	resultHeight := imath.Scale(po.Height, po.Dpr)
+	resultWidth, resultHeight := resultSize(po)
 
 	if !po.Extend.Enabled || (resultWidth <= img.Width() && resultHeight <= img.Height()) {
 		return nil

processing/prepare.go

@@ -98,6 +98,9 @@ func calcScale(width, height int, po *options.ProcessingOptions, imgtype imagety
 		}
 	}
 
+	wshrink /= po.ZoomWidth
+	hshrink /= po.ZoomHeight
+
 	if !po.Enlarge && imgtype != imagetype.SVG {
 		if wshrink < 1 {
 			hshrink /= wshrink

processing/result_size.go

@@ -0,0 +1,13 @@
+package processing
+
+import (
+	"github.com/imgproxy/imgproxy/v3/imath"
+	"github.com/imgproxy/imgproxy/v3/options"
+)
+
+func resultSize(po *options.ProcessingOptions) (int, int) {
+	resultWidth := imath.Scale(po.Width, po.Dpr*po.ZoomWidth)
+	resultHeight := imath.Scale(po.Height, po.Dpr*po.ZoomHeight)
+
+	return resultWidth, resultHeight
+}