Bilinear interpolation: Difference between revisions
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{{draft task}}
[[wp:Bilinear interpolation|Bilinear interpolation]] is linear interpolation in 2 dimensions, and is typically used for image scaling and for 2D finite element analysis.
;Task:
Open an image file, enlarge it by 60% using bilinear interpolation, then either display the result or save the result to a file.
<br><br>
=={{header|Action!}}==
In the following solution the input file [https://gitlab.com/amarok8bit/action-rosetta-code/-/blob/master/source/lena30g.PPM lena30g.PPM] is loaded from H6 drive. Altirra emulator automatically converts CR/LF character from ASCII into 155 character in ATASCII charset used by Atari 8-bit computer when one from H6-H10 hard drive under DOS 2.5 is used.
{{libheader|Action! Bitmap tools}}
{{libheader|Action! Tool Kit}}
{{libheader|Action! Real Math}}
<syntaxhighlight lang="action!">INCLUDE "H6:REALMATH.ACT"
INCLUDE "H6:LOADPPM5.ACT"
PROC PutBigPixel(INT x,y BYTE col)
IF x>=0 AND x<=79 AND y>=0 AND y<=47 THEN
y==LSH 2
col==RSH 4
IF col<0 THEN col=0
ELSEIF col>15 THEN col=15 FI
Color=col
Plot(x,y)
DrawTo(x,y+3)
FI
RETURN
PROC DrawImage(GrayImage POINTER image INT x,y)
INT i,j
BYTE c
FOR j=0 TO image.gh-1
DO
FOR i=0 TO image.gw-1
DO
c=GetGrayPixel(image,i,j)
PutBigPixel(x+i,y+j,c)
OD
OD
RETURN
PROC Lerp(REAL POINTER s,e,t,res)
REAL tmp1,tmp2
RealSub(e,s,tmp1) ;tmp1=e-s
RealMult(tmp1,t,tmp2) ;tmp2=(e-s)*t
RealAdd(s,tmp2,res) ;res=s+(e-s)*t
RETURN
PROC BilinearInterpolation(GrayImage POINTER src,dst)
INT i,j,x,y,c
REAL mx,my,rx,ry,fx,fy,tmp1,tmp2,tmp3,r00,r01,r10,r11
BYTE c00,c01,c10,c11
IntToReal(src.gw-1,tmp1) ;tmp1=src.width-1
IntToReal(dst.gw,tmp2) ;tmp2=dst.width
RealDiv(tmp1,tmp2,mx) ;mx=(src.width-1)/dst.width
IntToReal(src.gh-1,tmp1) ;tmp1=src.height-1
IntToReal(dst.gh,tmp2) ;tmp2=dst.height
RealDiv(tmp1,tmp2,my) ;my=(src.height-1)/dst.height
FOR j=0 TO dst.gh-1
DO
IntToReal(j,tmp1) ;tmp=j
RealMult(tmp1,my,ry) ;ry=j*my
y=Floor(ry)
IntToReal(y,tmp1) ;tmp1=floor(ry)
RealSub(ry,tmp1,fy) ;fy=frac(ry)
FOR i=0 TO dst.gw-1
DO
IntToReal(i,tmp1) ;tmp=i
RealMult(tmp1,mx,rx) ;rx=i*mx
x=Floor(rx)
IntToReal(x,tmp1) ;tmp1=floor(rx)
RealSub(rx,tmp1,fx) ;fx=frac(rx)
c00=GetGrayPixel(src,x,y)
c01=GetGrayPixel(src,x,y+1)
c10=GetGrayPixel(src,x+1,y)
c11=GetGrayPixel(src,x+1,y+1)
IntToReal(c00,r00)
IntToReal(c01,r01)
IntToReal(c10,r10)
IntToReal(c11,r11)
Lerp(r00,r10,fx,tmp1)
Lerp(r01,r11,fx,tmp2)
Lerp(tmp1,tmp2,fy,tmp3)
c=RealToInt(tmp3)
IF c<0 THEN
c=0
ELSEIF c>255 THEN
c=255
FI
SetGrayPixel(dst,i,j,c)
OD
OD
RETURN
PROC Main()
BYTE CH=$02FC ;Internal hardware value for last key pressed
BYTE ARRAY data30x30(900),data48x48(2304)
GrayImage im30x30,im48x48
Put(125) PutE() ;clear the screen
MathInit()
InitGrayImage(im30x30,30,30,data30x30)
InitGrayImage(im48x48,48,48,data48x48)
PrintE("Loading source image...")
LoadPPM5(im30x30,"H6:LENA30G.PPM")
PrintE("Bilinear interpolation...")
BilinearInterpolation(im30x30,im48x48)
Graphics(9)
DrawImage(im30x30,0,0)
DrawImage(im48x48,32,0)
DO UNTIL CH#$FF OD
CH=$FF
RETURN</syntaxhighlight>
{{out}}
[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Bilinear_interpolation.png Screenshot from Atari 8-bit computer]
=={{header|C}}==
<
typedef struct {
uint32_t *pixels;
Line 16 ⟶ 134:
return image->pixels[(y*image->w)+x];
}
float max(float a, float b) { return (a < b) ? a : b; };
float lerp(float s, float e, float t){return s+(e-s)*t;}
float blerp(float c00, float c10, float c01, float c11, float tx, float ty){
Line 31 ⟶ 151:
x = 0; y++;
}
//float gx = x / (float)(newWidth) * (src->w - 1);
//float gy = y / (float)(newHeight) * (src->h - 1);
// Image should be clamped at the edges and not scaled.
float gx = max(x / (float)(newWidth) * (src->w) - 0.5f, src->w - 1);
float gy = max(y / (float)(newHeight) * (src->h) - 0.5, src->h - 1);
int gxi = (int)gx;
int gyi = (int)gy;
Line 47 ⟶ 170:
putpixel(dst,x, y, result);
}
}</
=={{header|C sharp|C#}}==
{{trans|Java}}
Seems to have some artifacting in the output, but the image is at least recognizable.
<syntaxhighlight lang="csharp">using System;
using System.Drawing;
namespace BilinearInterpolation {
class Program {
private static float Lerp(float s, float e, float t) {
return s + (e - s) * t;
}
private static float Blerp(float c00, float c10, float c01, float c11, float tx, float ty) {
return Lerp(Lerp(c00, c10, tx), Lerp(c01, c11, tx), ty);
}
private static Image Scale(Bitmap self, float scaleX, float scaleY) {
int newWidth = (int)(self.Width * scaleX);
int newHeight = (int)(self.Height * scaleY);
Bitmap newImage = new Bitmap(newWidth, newHeight, self.PixelFormat);
for (int x = 0; x < newWidth; x++) {
for (int y = 0; y < newHeight; y++) {
float gx = ((float)x) / newWidth * (self.Width - 1);
float gy = ((float)y) / newHeight * (self.Height - 1);
int gxi = (int)gx;
int gyi = (int)gy;
Color c00 = self.GetPixel(gxi, gyi);
Color c10 = self.GetPixel(gxi + 1, gyi);
Color c01 = self.GetPixel(gxi, gyi + 1);
Color c11 = self.GetPixel(gxi + 1, gyi + 1);
int red = (int)Blerp(c00.R, c10.R, c01.R, c11.R, gx - gxi, gy - gyi);
int green = (int)Blerp(c00.G, c10.G, c01.G, c11.G, gx - gxi, gy - gyi);
int blue = (int)Blerp(c00.B, c10.B, c01.B, c11.B, gx - gxi, gy - gyi);
Color rgb = Color.FromArgb(red, green, blue);
newImage.SetPixel(x, y, rgb);
}
}
return newImage;
}
static void Main(string[] args) {
Image newImage = Image.FromFile("Lenna100.jpg");
if (newImage is Bitmap oi) {
Image result = Scale(oi, 1.6f, 1.6f);
result.Save("Lenna100_larger.jpg");
} else {
Console.WriteLine("Could not open the source file.");
}
}
}
}</syntaxhighlight>
=={{header|D}}==
This uses the module from the Grayscale Image task.
{{trans|C}}
<
/// Currently this accepts only a Grayscale image, for simplicity.
Line 100 ⟶ 276:
im.rescaleGray(0.3, 0.1).savePGM("lena_smaller.pgm");
im.rescaleGray(1.3, 1.8).savePGM("lena_larger.pgm");
}</
=={{header|F sharp|F#}}==
{{trans|C#}}
<syntaxhighlight lang="fsharp">open System
open System.Drawing
let lerp (s:float) (e:float) (t:float) =
s + (e - s) * t
let blerp c00 c10 c01 c11 tx ty =
lerp (lerp c00 c10 tx) (lerp c01 c11 tx) ty
let scale (self:Bitmap) (scaleX:float) (scaleY:float) =
let newWidth = int ((float self.Width) * scaleX)
let newHeight = int ((float self.Height) * scaleY)
let newImage = new Bitmap(newWidth, newHeight, self.PixelFormat)
for x in 0..newWidth-1 do
for y in 0..newHeight-1 do
let gx = (float x) / (float newWidth) * (float (self.Width - 1))
let gy = (float y) / (float newHeight) * (float (self.Height - 1))
let gxi = int gx
let gyi = int gy
let c00 = self.GetPixel(gxi, gyi)
let c10 = self.GetPixel(gxi + 1, gyi)
let c01 = self.GetPixel(gxi, gyi + 1)
let c11 = self.GetPixel(gxi + 1, gyi + 1)
let red = int (blerp (float c00.R) (float c10.R) (float c01.R) (float c11.R) (gx - (float gxi)) (gy - (float gyi)))
let green = int (blerp (float c00.G) (float c10.G) (float c01.G) (float c11.G) (gx - (float gxi)) (gy - (float gyi)))
let blue = int (blerp (float c00.B) (float c10.B) (float c01.B) (float c11.B) (gx - (float gxi)) (gy - (float gyi)))
let rgb = Color.FromArgb(red, green, blue)
newImage.SetPixel(x, y, rgb)
newImage
// Taken from https://stackoverflow.com/a/2362114
let castAs<'T when 'T : null> (o:obj) =
match o with
| :? 'T as res -> res
| _ -> Unchecked.defaultof<'T>
[<EntryPoint>]
let main _ =
let newImage = Image.FromFile("Lenna100.jpg")
let oi = castAs<Bitmap>(newImage)
if oi = null then
Console.WriteLine("Could not open the source file.")
else
let result = scale oi 1.6 1.6
result.Save("Lenna100_larger.jpg")
0 // return an integer exit code</syntaxhighlight>
=={{header|Go}}==
{{trans|C}}
(and also just using
<code>[https://godoc.org/golang.org/x/image/draw#BiLinear draw.BiLinear]</code>
from the <code>golang.org/x/image/draw</code> pacakge).
<syntaxhighlight lang="go">package main
import (
"image"
"image/color"
"image/jpeg"
"log"
"math"
"os"
"golang.org/x/image/draw"
)
func scale(dst draw.Image, src image.Image) {
sr := src.Bounds()
dr := dst.Bounds()
mx := float64(sr.Dx()-1) / float64(dr.Dx())
my := float64(sr.Dy()-1) / float64(dr.Dy())
for x := dr.Min.X; x < dr.Max.X; x++ {
for y := dr.Min.Y; y < dr.Max.Y; y++ {
gx, tx := math.Modf(float64(x) * mx)
gy, ty := math.Modf(float64(y) * my)
srcX, srcY := int(gx), int(gy)
r00, g00, b00, a00 := src.At(srcX, srcY).RGBA()
r10, g10, b10, a10 := src.At(srcX+1, srcY).RGBA()
r01, g01, b01, a01 := src.At(srcX, srcY+1).RGBA()
r11, g11, b11, a11 := src.At(srcX+1, srcY+1).RGBA()
result := color.RGBA64{
R: blerp(r00, r10, r01, r11, tx, ty),
G: blerp(g00, g10, g01, g11, tx, ty),
B: blerp(b00, b10, b01, b11, tx, ty),
A: blerp(a00, a10, a01, a11, tx, ty),
}
dst.Set(x, y, result)
}
}
}
func lerp(s, e, t float64) float64 { return s + (e-s)*t }
func blerp(c00, c10, c01, c11 uint32, tx, ty float64) uint16 {
return uint16(lerp(
lerp(float64(c00), float64(c10), tx),
lerp(float64(c01), float64(c11), tx),
ty,
))
}
func main() {
src, err := readImage("Lenna100.jpg")
if err != nil {
log.Fatal(err)
}
sr := src.Bounds()
dr := image.Rect(0, 0, sr.Dx()*16/10, sr.Dy()*16/10)
dst := image.NewRGBA(dr)
// Using the above bilinear interpolation code:
scale(dst, src)
err = writeJPEG(dst, "Lenna100_larger.jpg")
if err != nil {
log.Fatal(err)
}
// Using the golang.org/x/image/draw package
// (which also provides other iterpolators).
draw.BiLinear.Scale(dst, dr, src, sr, draw.Src, nil)
err = writeJPEG(dst, "Lenna100_larger.draw.jpg")
if err != nil {
log.Fatal(err)
}
}
func readImage(filename string) (image.Image, error) {
f, err := os.Open(filename)
if err != nil {
return nil, err
}
defer f.Close() // nolint: errcheck
m, _, err := image.Decode(f)
return m, err
}
func writeJPEG(m image.Image, filename string) error {
f, err := os.Create(filename)
if err != nil {
return err
}
err = jpeg.Encode(f, m, nil)
if cerr := f.Close(); err == nil {
err = cerr
}
return err
}</syntaxhighlight>
=={{header|J}}==
<syntaxhighlight lang="j">
Note 'FEA'
Here we develop a general method to generate isoparametric interpolants.
Line 163 ⟶ 485:
shape_function =: 1 , ] , */
COEFFICIENTS =: (=i.4) %. shape_function"1 CORNERS
shape_functions =: COEFFICIENTS mp~ shape_function
interpolate =: mp shape_functions
</syntaxhighlight>
<pre>
Note 'demonstrate the interpolant with a saddle'
Line 178 ⟶ 500:
SADDLE =: 1 2 2.2 0.7 interpolate"_ 1 GRID
viewmat SADDLE
assert 0.7 2.2 -: (<./ , >./) , SADDLE
</pre>
[[Image:J_bilinear_interpolant.jpg]]
Let n mean shape function, C mean constants, i mean interpolant, and the three digits meaning dimensionality, number of corners, and (in base 36) the number of nodes we construct various linear and quadratic interpolants in 1, 2, and 3 dimensions as
<syntaxhighlight lang="j">
Note 'Some elemental information'
Node order
1D:
0 2 1
2D:
2 7 3
5 8 6 Node 8 at origin, Node 3 at (1,1)
0 4 1
Names for shape functions and constants:
n249: n means shape function, 2 dimensions, 4 corners (quadrilateral), 9 nodes
C244: C constants for 2 dimensions, 4 corners (quadrilateral), 4 nodes
3D
At z = _1 z = 1 z = 0
2 b 3 6 j 7 e o f
9 k a h p i m q n
0 8 1 4 g 5 c l d
)
mp =: ($: |:) : (+/ .*) NB. A Atranspose : matrix product A B
identity =: =@:i. NB. generate identity matrix
NB. 1D
NB. master nodes
N1 =: ,._1 1 0x
NB. form of shape functions
n122 =: 1 , ]
n123 =: [: , ^/&(i.3)
NB. constants
C122 =: x:inv@:(x:@:identity@:# %. n122"1)2{.N1
C123 =: x:inv@:(x:@:identity@:# %. n123"1)3{.N1
NB. interpolants
i122 =: mp (C122 mp~ n122)
i123 =: mp (C123 mp~ n123)
NB. 2D
NB. nodes are arranged 4&{. are the corners, 8&{. the corners and edges, ] include the center.
N2 =: 336330 A.-.3x#.inv i.*:3 NB. 336330 (-: A.) 8 2 6 0 5 7 1 3 4
NB. terms of shape functions
n244 =: [: , [: *// ^/&(i.2) NB. all linear combinations
n248 =: }:@:n249 NB. exclude (xi eta)^2
n249 =: [: , [: *// ^/&(i.3) NB. all quadratic combinations
NB. constants
C244 =: x:inv@:(x:@:identity@:# %. n244"1)4{.N2 NB. serendipity
C248 =: x:inv@:(x:@:identity@:# %. n248"1)8{.N2 NB. serendipity
C249 =: x:inv@:(x:@:identity@:# %. n249"1)9{.N2 NB. non-serendipity
NB. interpolants
i244 =: mp (C244 mp~ n244)
i248 =: mp (C248 mp~ n248)
i249 =: mp (C249 mp~ n249)
NB. 3D
N3 =: 267337661061030402017459663x A.<:3#.inv i.3^3 NB. 267337661061030402017459663x (-: A.) 0 18 6 24 2 20 8 26 9 3 21 15 1 19 7 25 11 5 23 17 12 10 4 22 16 14 13
NB. corners
n388 =: [: , [: *// 1 , ] NB. all linear combinations
Note 'simplification not yet apparent to me'
combinations =: 4 : 0
if. x e. 0 1 do. z=.<((x!y),x)$ i.y
else. t=. |.(<.@-:)^:(i.<. 2^.x)x
z=.({.t) ([:(,.&.><@;\.)/ >:@-~[\i.@]) ({.t)+y-x
for_j. 2[\t do.
z=.([ ;@:(<"1@[ (,"1 ({.j)+])&.> ])&.> <@;\.({&.><)~ (1+({.j)-~{:"1)&.>) z
if. 2|{:j do. z=.(i.1+y-x)(,.>:)&.> <@;\.z end.
end.
end.
;z
NB.)
n38k =: 1 , ] , */"1@:((2 combinations 3)&{) , *: , (1&, * */) , ,@:(*:@:|. (*"0 1) (2 combinations 3)&{) NB. include mid-edge nodes
)
n38q =: }:@:n38r NB. include mid-face nodes, all quadratic combinations but (xyz)^2
n38r =: [: , [: *// ^/&(i.3) NB. now this is simple! 3*3*3 nodal grid.
C388 =: x:inv@:(x:@:identity@:# %. n388"1)8{.N3
NB.C38k =: x:inv@:(x:@:identity@:# %. n38k"1)36bk{.N3
C38q =: x:inv@:(x:@:identity@:# %. x:@:n38q"1)36bq{.N3
C38r =: x:inv@:(x:@:identity@:# %. x:@:n38r"1)36br{.N3
i388 =: mp (C388 mp~ n388)
NB.i38k =: mp (C38k mp~ n38k)
i38q =: mp (C38r mp~ n38r)
i38r =: mp (C38r mp~ n38r)
</syntaxhighlight>
=={{header|Java}}==
{{trans|Kotlin}}
<syntaxhighlight lang="java">import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
public class BilinearInterpolation {
/* gets the 'n'th byte of a 4-byte integer */
private static int get(int self, int n) {
return (self >> (n * 8)) & 0xFF;
}
private static float lerp(float s, float e, float t) {
return s + (e - s) * t;
}
private static float blerp(final Float c00, float c10, float c01, float c11, float tx, float ty) {
return lerp(lerp(c00, c10, tx), lerp(c01, c11, tx), ty);
}
private static BufferedImage scale(BufferedImage self, float scaleX, float scaleY) {
int newWidth = (int) (self.getWidth() * scaleX);
int newHeight = (int) (self.getHeight() * scaleY);
BufferedImage newImage = new BufferedImage(newWidth, newHeight, self.getType());
for (int x = 0; x < newWidth; ++x) {
for (int y = 0; y < newHeight; ++y) {
float gx = ((float) x) / newWidth * (self.getWidth() - 1);
float gy = ((float) y) / newHeight * (self.getHeight() - 1);
int gxi = (int) gx;
int gyi = (int) gy;
int rgb = 0;
int c00 = self.getRGB(gxi, gyi);
int c10 = self.getRGB(gxi + 1, gyi);
int c01 = self.getRGB(gxi, gyi + 1);
int c11 = self.getRGB(gxi + 1, gyi + 1);
for (int i = 0; i <= 2; ++i) {
float b00 = get(c00, i);
float b10 = get(c10, i);
float b01 = get(c01, i);
float b11 = get(c11, i);
int ble = ((int) blerp(b00, b10, b01, b11, gx - gxi, gy - gyi)) << (8 * i);
rgb = rgb | ble;
}
newImage.setRGB(x, y, rgb);
}
}
return newImage;
}
public static void main(String[] args) throws IOException {
File lenna = new File("Lenna100.jpg");
BufferedImage image = ImageIO.read(lenna);
BufferedImage image2 = scale(image, 1.6f, 1.6f);
File lenna2 = new File("Lenna100_larger.jpg");
ImageIO.write(image2, "jpg", lenna2);
}
}</syntaxhighlight>
=={{header|Julia}}==
<syntaxhighlight lang="julia">using Images, FileIO, Interpolations
function enlarge(A::Matrix, factor::AbstractFloat)
lx, ly = size(A)
nx, ny = round.(Int, factor .* (lx, ly))
vx, vy = LinRange(1, lx, nx), LinRange(1, ly, ny)
itp = interpolate(A, BSpline(Linear()))
return itp(vx, vy)
end
A = load("data/lenna100.jpg") |> Matrix{RGB{Float64}};
Alarge = enlarge(A, 1.6);
save("data/lennaenlarged.jpg", Alarge)
</syntaxhighlight>
=={{header|Kotlin}}==
{{trans|C}}
<syntaxhighlight lang="scala">// version 1.2.21
import java.io.File
import java.awt.image.BufferedImage
import javax.imageio.ImageIO
/* gets the 'n'th byte of a 4-byte integer */
operator fun Int.get(n: Int) = (this shr (n * 8)) and 0xFF
fun lerp(s: Float, e: Float, t: Float) = s + (e - s) * t
fun blerp(c00: Float, c10: Float, c01: Float, c11: Float, tx: Float, ty: Float) =
lerp(lerp(c00, c10, tx), lerp(c01,c11, tx), ty)
fun BufferedImage.scale(scaleX: Float, scaleY: Float): BufferedImage {
val newWidth = (width * scaleX).toInt()
val newHeight = (height * scaleY).toInt()
val newImage = BufferedImage(newWidth, newHeight, type)
for (x in 0 until newWidth) {
for (y in 0 until newHeight) {
val gx = x.toFloat() / newWidth * (width - 1)
val gy = y.toFloat() / newHeight * (height - 1)
val gxi = gx.toInt()
val gyi = gy.toInt()
var rgb = 0
val c00 = getRGB(gxi, gyi)
val c10 = getRGB(gxi + 1, gyi)
val c01 = getRGB(gxi, gyi + 1)
val c11 = getRGB(gxi + 1, gyi + 1)
for (i in 0..2) {
val b00 = c00[i].toFloat()
val b10 = c10[i].toFloat()
val b01 = c01[i].toFloat()
val b11 = c11[i].toFloat()
val ble = blerp(b00, b10, b01, b11, gx - gxi, gy - gyi).toInt() shl (8 * i)
rgb = rgb or ble
}
newImage.setRGB(x, y, rgb)
}
}
return newImage
}
fun main(args: Array<String>) {
val lenna = File("Lenna100.jpg") // from the Percentage difference between images task
val image = ImageIO.read(lenna)
val image2 = image.scale(1.6f, 1.6f)
val lenna2 = File("Lenna100_larger.jpg")
ImageIO.write(image2, "jpg", lenna2)
}</syntaxhighlight>
=={{header|Mathematica}}/{{header|Wolfram Language}}==
<syntaxhighlight lang="mathematica">ImageResize[Import["http://www.rosettacode.org/mw/title.png"], Scaled[1.6], Resampling -> "Linear"]</syntaxhighlight>
{{out}}
Shows a downloaded image that is 60% enlarged.
=={{header|Nim}}==
{{trans|F#}}
{{libheader|imageman}}
<syntaxhighlight lang="nim">import imageman
func lerp(s, e, t: float): float =
s + (e - s) * t
func blerp(c00, c10, c01, c11, tx, ty: float): float =
lerp(lerp(c00, c10, tx), lerp(c01, c11, tx), ty)
func scale(img: Image; scaleX, scaleY: float): Image =
let newWidth = (img.width.toFloat * scaleX).toInt
let newHeight = (img.height.toFloat * scaleY).toInt
result = initImage[ColorRGBU](newWidth, newHeight)
for x in 0..<newWidth:
for y in 0..<newHeight:
let gx = x * (img.width - 1) / newWidth
let gy = y * (img.height - 1) / newHeight
let gxi = gx.int
let gyi = gy.int
let gxf = gx - float(gxi)
let gyf = gy - float(gyi)
let c00 = img[gxi, gyi]
let c10 = img[gxi + 1, gyi]
let c01 = img[gxi, gyi + 1]
let c11 = img[gxi + 1, gyi + 1]
let red = blerp(float(c00[0]), float(c10[0]), float(c01[0]), float(c11[0]), gxf, gyf).toInt
let green = blerp(float(c00[1]), float(c10[1]), float(c01[1]), float(c11[1]), gxf, gyf).toInt
let blue = blerp(float(c00[2]), float(c10[2]), float(c01[2]), float(c11[2]), gxf, gyf).toInt
result[x, y] = ColorRGBU([byte(red), byte(green), byte(blue)])
when isMainModule:
let image = loadImage[ColorRGBU]("Lenna100.jpg")
let newImage = image.scale(1.6, 1.6)
newImage.saveJPEG("Lenna100_bilinear.jpg")</syntaxhighlight>
=={{header|Perl}}==
<syntaxhighlight lang="perl">use strict;
use warnings;
use GD;
my $image = GD::Image->newFromPng('color_wheel.png');
$image->interpolationMethod( ['GD_BILINEAR_FIXED'] );
my($width,$height) = $image->getBounds();
my $image2 = $image->copyScaleInterpolated( 1.6*$width, 1.6*$height );
$image2->_file('color_wheel_interpolated.png');</syntaxhighlight>
Compare offsite images: [https://github.com/SqrtNegInf/Rosettacode-Perl5-Smoke/blob/master/ref/color_wheel.png color_wheel.png] vs.
[https://github.com/SqrtNegInf/Rosettacode-Perl5-Smoke/blob/master/ref/color_wheel_interpolated.png color_wheel_interpolated.png]
=={{header|Phix}}==
{{libheader|Phix/pGUI}}
Gui app with slider for between 2 and 200% scaling. Various bits of this code scavenged from C#/Go/Kotlin/Wikipedia.
<syntaxhighlight lang="phix">-- demo\rosetta\Bilinear_interpolation.exw
include pGUI.e
function interpolate(atom s, e, f)
--
-- s,e are the start and end values (one original pixel apart),
-- f is a fraction of some point between them, 0(==s)..1(==e).
-- eg s=91 (f=0.2) e=101, we want 0.8 of the 91 + 0.2 of 101,
-- aka if f is 4 times closer to s than e, we want 4 times as
-- much of s as we want of e, with sum(fractions_taken)==1.
--
return s + (e-s)*f -- aka s*(1-f) + e*f
end function
function bilinear(integer c00, c10, c01, c11, atom fx, fy)
--
-- for some output pixel, we have calculated the exact point
-- on the original, and extracted the four pixels surrounding
-- that, with fx,fy as the fractional x,y part of the 1x1 box.
-- Like a capital H, we want some fraction on the left and the
-- same on the right, then some fraction along the horizontal.
-- It would be equivalent to do top/bottom then the vertical,
-- which is handy since I am no longer certain which of those
-- the following actually does, especially since we got the
-- pixels from original[y,x] rather than original[x,y], and
-- imImage and IupImage have {0,0} in different corners - but
-- the output looks pretty good, and I think you would easily
-- notice were this even slightly wrong, and in fact an early
-- accidental typo of r10/r01 indeed proved very evident.
--
atom left = interpolate(c00,c10,fx),
right = interpolate(c01,c11,fx)
return floor(interpolate(left,right,fy))
end function
function scale_image(imImage img, atom scaleX, scaleY)
integer width = im_width(img),
height = im_height(img),
new_width = floor(width * scaleX)-1,
new_height = floor(height * scaleY)-1
atom mx = (width-1)/new_width,
my = (height-1)/new_height
sequence original = repeat(repeat(0,width),height)
sequence new_image = repeat(repeat(0,new_width),new_height)
-- Extract the original pixels from the image [about
-- twice as fast as 4*im_pixel() in the main loop.]
for y=height-1 to 0 by -1 do
for x=0 to width-1 do
original[height-y,x+1] = im_pixel(img, x, y)
end for
end for
for x=0 to new_width-1 do
for y=0 to new_height-1 do
atom ax = x*mx, -- map onto original
ay = y*my
integer ix = floor(ax), -- top left
iy = floor(ay)
ax -= ix -- fraction of the 1x1 box
ay -= iy
integer {r00,g00,b00} = original[iy+1,ix+1],
{r10,g10,b10} = original[iy+1,ix+2],
{r01,g01,b01} = original[iy+2,ix+1],
{r11,g11,b11} = original[iy+2,ix+2],
r = bilinear(r00,r10,r01,r11,ax,ay),
g = bilinear(g00,g10,g01,g11,ax,ay),
b = bilinear(b00,b10,b01,b11,ax,ay)
new_image[y+1,x+1] = {r,g,b}
end for
end for
new_image = flatten(new_image) -- (as needed by IupImageRGB)
Ihandle new_img = IupImageRGB(new_width, new_height, new_image)
return new_img
end function
IupOpen()
constant w = machine_word()
atom pError = allocate(w)
imImage im1 = imFileImageLoadBitmap("Lena.ppm",0,pError)
if im1=NULL then
?{"error opening image",peekNS(pError,w,1)}
{} = wait_key()
abort(0)
end if
Ihandle dlg,
scale = IupValuator(NULL,"MIN=2,MAX=200,VALUE=160"),
redraw = IupButton("redraw (160%)")
Ihandln image1 = IupImageFromImImage(im1),
image2 = scale_image(im1,1.6,1.6),
label1 = IupLabel(),
label2 = IupLabel()
IupSetAttributeHandle(label1, "IMAGE", image1)
IupSetAttributeHandle(label2, "IMAGE", image2)
function valuechanged_cb(Ihandle /*scale*/)
atom v = IupGetDouble(scale,"VALUE")
IupSetStrAttribute(redraw,"TITLE","redraw (%d%%)",{v})
return IUP_DEFAULT
end function
IupSetCallback(scale,"VALUECHANGED_CB",Icallback("valuechanged_cb"))
function redraw_cb(Ihandle /*redraw*/)
IupSetAttributeHandle(label2, "IMAGE", NULL)
image2 = IupDestroy(image2)
atom v = IupGetDouble(scale,"VALUE")/100
image2 = scale_image(im1,v,v)
IupSetAttributeHandle(label2, "IMAGE", image2)
IupSetAttribute(dlg,"SIZE",NULL)
IupRefresh(dlg)
return IUP_DEFAULT
end function
IupSetCallback(redraw,"ACTION",Icallback("redraw_cb"))
dlg = IupDialog(IupVbox({IupHbox({scale, redraw}),
IupHbox({label1, label2})}))
IupSetAttribute(dlg, "TITLE", "Bilinear interpolation")
IupShow(dlg)
IupMainLoop()
IupClose()</syntaxhighlight>
=={{header|Python}}==
Of course, it is much faster to use PIL, Pillow or SciPy to resize an image than to rely on this code.
<syntaxhighlight lang="python">#!/bin/python
import numpy as np
from scipy.misc import imread, imshow
from scipy import ndimage
def GetBilinearPixel(imArr, posX, posY):
out = []
#Get integer and fractional parts of numbers
modXi = int(posX)
modYi = int(posY)
modXf = posX - modXi
modYf = posY - modYi
modXiPlusOneLim = min(modXi+1,imArr.shape[1]-1)
modYiPlusOneLim = min(modYi+1,imArr.shape[0]-1)
#Get pixels in four corners
for chan in range(imArr.shape[2]):
bl = imArr[modYi, modXi, chan]
br = imArr[modYi, modXiPlusOneLim, chan]
tl = imArr[modYiPlusOneLim, modXi, chan]
tr = imArr[modYiPlusOneLim, modXiPlusOneLim, chan]
#Calculate interpolation
b = modXf * br + (1. - modXf) * bl
t = modXf * tr + (1. - modXf) * tl
pxf = modYf * t + (1. - modYf) * b
out.append(int(pxf+0.5))
return out
if __name__=="__main__":
im = imread("test.jpg", mode="RGB")
enlargedShape = list(map(int, [im.shape[0]*1.6, im.shape[1]*1.6, im.shape[2]]))
enlargedImg = np.empty(enlargedShape, dtype=np.uint8)
rowScale = float(im.shape[0]) / float(enlargedImg.shape[0])
colScale = float(im.shape[1]) / float(enlargedImg.shape[1])
for r in range(enlargedImg.shape[0]):
for c in range(enlargedImg.shape[1]):
orir = r * rowScale #Find position in original image
oric = c * colScale
enlargedImg[r, c] = GetBilinearPixel(im, oric, orir)
imshow(enlargedImg)
</syntaxhighlight>
=={{header|Racket}}==
This mimics the Wikipedia example.
<
(require images/flomap)
Line 205 ⟶ 984:
(λ (k x y)
(flomap-bilinear-ref
fm k (+ 1/2 (/ x 250)) (+ 1/2 (/ y 250))))))</
=={{header|Raku}}==
(formerly Perl 6)
<syntaxhighlight lang="raku" line>#!/usr/bin/env perl6
use v6;
use GD::Raw;
# Reference:
# https://github.com/dagurval/perl6-gd-raw
my $fh1 = fopen('./Lenna100.jpg', "rb") or die;
my $img1 = gdImageCreateFromJpeg($fh1);
my $fh2 = fopen('./Lenna100-larger.jpg',"wb") or die;
my $img1X = gdImageSX($img1);
my $img1Y = gdImageSY($img1);
my $NewX = $img1X * 1.6;
my $NewY = $img1Y * 1.6;
gdImageSetInterpolationMethod($img1, +GD_BILINEAR_FIXED);
my $img2 = gdImageScale($img1, $NewX.ceiling, $NewY.ceiling);
gdImageJpeg($img2,$fh2,-1);
gdImageDestroy($img1);
gdImageDestroy($img2);
fclose($fh1);
fclose($fh2);
</syntaxhighlight>
{{out}}
<pre>file Lenna100*
Lenna100.jpg: JPEG image data, JFIF standard 1.01, resolution (DPI), density 72x72, segment length 16, baseline, precision 8, 512x512, frames 3
Lenna100-larger.jpg: JPEG image data, JFIF standard 1.01, resolution (DPI), density 96x96, segment length 16, comment: "CREATOR: gd-jpeg v1.0 (using IJG JPEG v80), default quality", baseline, precision 8, 820x820, frames 3</pre>
=={{header|Scala}}==
===Imperative solution===
<syntaxhighlight lang="scala">import java.awt.image.BufferedImage
import java.io.{File, IOException}
import javax.imageio.ImageIO
object BilinearInterpolation {
@throws[IOException]
def main(args: Array[String]): Unit = {
val lenna = new File("Lenna100.jpg")
val image = ImageIO.read(lenna)
val image2 = scale(image, 1.6f, 1.6f)
val lenna2 = new File("Lenna100_larger.jpg")
ImageIO.write(image2, "jpg", lenna2)
}
private def scale(self: BufferedImage, scaleX: Float, scaleY: Float) = {
val newWidth = (self.getWidth * scaleX).toInt
val newHeight = (self.getHeight * scaleY).toInt
val newImage = new BufferedImage(newWidth, newHeight, self.getType)
var x = 0
while (x < newWidth) {
var y = 0
while (y < newHeight) {
val gx = x.toFloat / newWidth * (self.getWidth - 1)
val gy = y.toFloat / newHeight * (self.getHeight - 1)
val gxi = gx.toInt
val gyi = gy.toInt
var rgb = 0
val c00 = self.getRGB(gxi, gyi)
val c10 = self.getRGB(gxi + 1, gyi)
val c01 = self.getRGB(gxi, gyi + 1)
val c11 = self.getRGB(gxi + 1, gyi + 1)
var i = 0
while (i <= 2) {
val b00 = get(c00, i)
val b10 = get(c10, i)
val b01 = get(c01, i)
val b11 = get(c11, i)
val ble = blerp(b00, b10, b01, b11, gx - gxi, gy - gyi).toInt << (8 * i)
rgb = rgb | ble
i += 1
}
newImage.setRGB(x, y, rgb)
y += 1
}
x += 1
}
newImage
}
/* gets the 'n'th byte of a 4-byte integer */
private def get(self: Int, n: Int) = (self >> (n * 8)) & 0xFF
private def blerp(c00: Float, c10: Float, c01: Float, c11: Float, tx: Float, ty: Float) = lerp(lerp(c00, c10, tx), lerp(c01, c11, tx), ty)
private def lerp(s: Float, e: Float, t: Float) = s + (e - s) * t
}</syntaxhighlight>
=={{header|Sidef}}==
{{trans|C}}
<syntaxhighlight lang="ruby">require('Imager')
func scale(img, scaleX, scaleY) {
var (width, height) = (img.getwidth, img.getheight)
var (newWidth, newHeight) = (int(width*scaleX), int(height*scaleY))
var out = %O<Imager>.new(xsize => newWidth, ysize => newHeight)
var lerp = { |s, e, t|
s + t*(e-s)
}
var blerp = { |c00, c10, c01, c11, tx, ty|
lerp(lerp(c00, c10, tx), lerp(c01, c11, tx), ty)
}
for x,y in (^newWidth ~X ^newHeight) {
var gxf = (x/newWidth * (width - 1))
var gyf = (y/newHeight * (height - 1))
var gx = gxf.int
var gy = gyf.int
var *c00 = img.getpixel(x => gx, y => gy ).rgba
var *c10 = img.getpixel(x => gx+1, y => gy ).rgba
var *c01 = img.getpixel(x => gx, y => gy+1).rgba
var *c11 = img.getpixel(x => gx+1, y => gy+1).rgba
var rgb = 3.of { |i|
blerp(c00[i], c10[i], c01[i], c11[i], gxf - gx, gyf - gy).int
}
out.setpixel(x => x, y => y, color => rgb)
}
return out
}
var img = %O<Imager>.new(file => "input.png")
var out = scale(img, 1.6, 1.6)
out.write(file => "output.png")</syntaxhighlight>
=={{header|Tcl}}==
This uses the polynomial expansion described in wikipedia, and draws the same example as illustrated in that page with a different pallette. It's not particularly fast - about 300ms for a 200x200 surface on an arbitrary machine.
The script below will show the computed image in a GUI frame, and present a button to save it.
<syntaxhighlight lang="tcl">
package require Tk
proc pixel {f} {
if {$f < 0} {
error "why is $f?"
}
set i [expr {0xff & entier(0xff*$f)}]
format #%02x%02x%02x $i [expr {255-$i}] 127
}
proc bilerp {im O X Y XY} {
set w [image width $im]
set h [image height $im]
set dx [expr {1.0/$w}]
set dy [expr {1.0/$h}]
set a0 $O
set a1 [expr {$X - $O}]
set a2 [expr {$Y - $O}]
set a3 [expr {$O + $XY - ($X + $Y)}]
for {set y 0} {$y < $h} {incr y} {
for {set x 0} {$x < $w} {incr x} {
set i [expr {$x * $dx}]
set j [expr {$y * $dy}]
set xv [expr {$a0 + $a1*$i + $a2*$j + $a3*$i*$j}]
set y [expr {$h - $y}] ;# invert for screen coords
$im put [pixel $xv] -to $x $y
}
}
}
proc save {im} {
set fn [tk_getSaveFile -defaultextension png]
if {$fn eq ""} return
set fd [open $fn wb]
puts -nonewline $fd [$im data -format png]
close $fd
tk_messageBox -message "Saved as $fn!"
}
set im [image create photo -width 200 -height 200]
puts [time {bilerp $im 0 1 1 0.5} 1]
pack [label .l1 -image $im]
pack [button .b -text "save" -command [list save $im]]
</syntaxhighlight>
=={{header|Visual Basic .NET}}==
{{trans|C#}}
<syntaxhighlight lang="vbnet">Imports System.Drawing
Module Module1
Function Lerp(s As Single, e As Single, t As Single) As Single
Return s + (e - s) * t
End Function
Function Blerp(c00 As Single, c10 As Single, c01 As Single, c11 As Single, tx As Single, ty As Single) As Single
Return Lerp(Lerp(c00, c10, tx), Lerp(c01, c11, tx), ty)
End Function
Function Scale(self As Bitmap, scaleX As Single, scaleY As Single) As Image
Dim newWidth = CInt(Math.Floor(self.Width * scaleX))
Dim newHeight = CInt(Math.Floor(self.Height * scaleY))
Dim newImage As New Bitmap(newWidth, newHeight, self.PixelFormat)
For x = 0 To newWidth - 1
For y = 0 To newHeight - 1
Dim gx = CSng(x) / newWidth * (self.Width - 1)
Dim gy = CSng(y) / newHeight * (self.Height - 1)
Dim gxi = CInt(Math.Floor(gx))
Dim gyi = CInt(Math.Floor(gy))
Dim c00 = self.GetPixel(gxi, gyi)
Dim c10 = self.GetPixel(gxi + 1, gyi)
Dim c01 = self.GetPixel(gxi, gyi + 1)
Dim c11 = self.GetPixel(gxi + 1, gyi + 1)
Dim red = CInt(Blerp(c00.R, c10.R, c01.R, c11.R, gx - gxi, gy - gyi))
Dim green = CInt(Blerp(c00.G, c10.G, c01.G, c11.G, gx - gxi, gy - gyi))
Dim blue = CInt(Blerp(c00.B, c10.B, c01.B, c11.B, gx - gxi, gy - gyi))
Dim rgb = Color.FromArgb(red, green, blue)
newImage.SetPixel(x, y, rgb)
Next
Next
Return newImage
End Function
Sub Main()
Dim newImage = Image.FromFile("Lenna100.jpg")
If TypeOf newImage Is Bitmap Then
Dim oi As Bitmap = newImage
Dim result = Scale(oi, 1.6, 1.6)
result.Save("Lenna100_larger.jpg")
Else
Console.WriteLine("Could not open the source file.")
End If
End Sub
End Module</syntaxhighlight>
=={{header|Wren}}==
{{trans|Kotlin}}
{{libheader|DOME}}
Note that currently DOME's ImageData class can only save files to disk in .png format.
<syntaxhighlight lang="wren">import "dome" for Window
import "graphics" for Canvas, Color, ImageData
import "math" for Math
/* gets the 'n'th byte of a 4-byte integer */
var GetByte = Fn.new { |i, n| (i >> (n * 8)) & 0xff }
var Blerp = Fn.new { |c00, c10, c01, c11, tx, ty|
return Math.lerp(Math.lerp(c00, tx, c10), ty, Math.lerp(c01, tx, c11))
}
var ColorToInt = Fn.new { |c| (c.r) + (c.g << 8) + (c.b << 16) + (c.a << 24) }
class BilinearInterpolation {
construct new(filename, filename2, scaleX, scaleY) {
Window.title = "Bilinear interpolation"
_img = ImageData.load(filename)
var newWidth = (_img.width * scaleX).floor
var newHeight = (_img.height * scaleY).floor
Window.resize(newWidth, newHeight)
Canvas.resize(newWidth, newHeight)
_img2 = ImageData.create(filename2, newWidth, newHeight)
_filename2 = filename2
}
init() {
scaleImage()
}
scaleImage() {
for (x in 0..._img2.width) {
for (y in 0..._img2.height) {
var gx = x / _img2.width * (_img.width - 1)
var gy = y / _img2.height * (_img.height - 1)
var gxi = gx.floor
var gyi = gy.floor
var rgb = 0
var c00 = _img.pget(gxi, gyi)
var c10 = _img.pget(gxi+1, gyi)
var c01 = _img.pget(gxi, gyi+1)
var c11 = _img.pget(gxi+1, gyi+1)
for (i in 0..3) {
var b00 = GetByte.call(ColorToInt.call(c00), i)
var b10 = GetByte.call(ColorToInt.call(c10), i)
var b01 = GetByte.call(ColorToInt.call(c01), i)
var b11 = GetByte.call(ColorToInt.call(c11), i)
var ble = Blerp.call(b00, b10, b01, b11, gx-gxi, gy-gyi).floor << (8 * i)
rgb = rgb | ble
}
var r = GetByte.call(rgb, 0)
var g = GetByte.call(rgb, 1)
var b = GetByte.call(rgb, 2)
var a = GetByte.call(rgb, 3)
_img2.pset(x, y, Color.rgb(r, g, b, a))
}
}
_img2.draw(0, 0)
_img2.saveToFile(_filename2)
}
update() {}
draw(alpha) {}
}
var Game = BilinearInterpolation.new("Lenna100.jpg", "Lenna100_larger.png", 1.6, 1.6)</syntaxhighlight>
=={{header|Yabasic}}==
{{trans|Nim}}
<syntaxhighlight lang="yabasic">// Rosetta Code problem: http://rosettacode.org/wiki/Bilinear_interpolation
// Adapted from Nim to Yabasic by Galileo, 01/2022
import ReadFromPPM2
sub lerp(s, e, t)
return s + (e - s) * t
end sub
sub blerp(c00, c10, c01, c11, tx, ty)
return lerp(lerp(c00, c10, tx), lerp(c01, c11, tx), ty)
end sub
sub scale(scaleX, scaleY)
local width, height, x, y, gx, gy, gxi, gyi, gxf, gyf, c00$, c10$, c01$, c11$
width = peek("winwidth")
height = peek("winheight")
let newWidth = int(width * scaleX)
let newHeight = int(height * scaleY)
dim result(newWidth, newHeight, 3)
for x = 1 to newWidth
for y = 1 to newHeight:
let gx = x * (width - 1) / newWidth
let gy = y * (height - 1) / newHeight
let gxi = int(gx)
let gyi = int(gy)
let gxf = gx - gxi
let gyf = gy - gyi
let c00$ = right$(getbit$(gxi, gyi, gxi, gyi), 6)
let c10$ = right$(getbit$(gxi + 1, gyi, gxi + 1, gyi), 6)
let c01$ = right$(getbit$(gxi, gyi + 1, gxi, gyi + 1), 6)
let c11$ = right$(getbit$(gxi + 1, gyi + 1, gxi + 1, gyi + 1), 6)
result(x, y, 1) = int(blerp(dec(left$(c00$, 2)), dec(left$(c10$, 2)), dec(left$(c01$, 2)), dec(left$(c11$, 2)), gxf, gyf))
result(x, y, 2) = int(blerp(dec(mid$(c00$, 3, 2)), dec(mid$(c10$, 3, 2)), dec(mid$(c01$, 3, 2)), dec(mid$(c11$, 3, 2)), gxf, gyf))
result(x, y, 3) = int(blerp(dec(right$(c00$, 2)), dec(right$(c10$, 2)), dec(right$(c01$, 2)), dec(right$(c11$, 2)), gxf, gyf))
next
next
end sub
readPPM("lena.ppm")
print "Be patient, please ..."
scale(1.6, 1.6)
close window
open window newWidth, newHeight
for x = 1 to newWidth
for y = 1 to newHeight
color result(x, y, 1), result(x, y, 2), result(x, y, 3)
dot x, y
next
next</syntaxhighlight>
=={{header|zkl}}==
{{trans|C}}
Uses the PPM class from http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#zkl.
Not fast enough to be called slow.
<syntaxhighlight lang="zkl">fcn lerp(s,e,t){ s + (e-s)*t; }
fcn blerp(c00,c10,c01,c11, tx,ty){ lerp(lerp(c00,c10,tx), lerp(c01,c11,tx),ty) }
fcn scale(src, scaleX,scaleY){
newWidth,newHeight := Int(scaleX*src.w), Int(scaleY*src.h);
dst:=PPM(newWidth,newHeight);
foreach y,x in ([0.0..newHeight-1],[0.0..newWidth-1]){
gx:=x/newWidth *(src.w-1);
gy:=y/newHeight *(src.h-1);
gxi,gyi:=Int(gx), Int(gy);
// cxy=RGB, cxy.toBigEndian(3)-->(R,G,B)
c00,c10 := src[gxi,gyi].toBigEndian(3), src[gxi+1,gyi].toBigEndian(3);
c01 := src[gxi,gyi+1] .toBigEndian(3);
c11 := src[gxi+1,gyi+1].toBigEndian(3);
dst[x,y] = (3).pump(Data(), // Data is a byte bucket
'wrap(i){ blerp(c00[i],c10[i],c01[i],c11[i], gx-gxi, gy-gyi) })
.toBigEndian(0,3);
}
dst
}</syntaxhighlight>
<syntaxhighlight lang="zkl">img:=PPM.readPPMFile("lena.ppm");
img2:=scale(img,1.5,1.5);
img2.write(File("lena1.5.ppm","wb"));
scale(img,0.5,0.5).write(File("lena.5.ppm","wb"));</syntaxhighlight>
{{out}}
http://www.zenkinetic.com/Images/RosettaCode/3Lenas.jpg
| |||