# HG changeset patch # User Sean Russell # Date 1340557173 14400 # Sun Jun 24 12:59:33 2012 -0400 # Node ID 63acf5de0980ae6c06988eb33024867bb7da2e6c # Parent 0000000000000000000000000000000000000000 Go version 1 diff --git a/README.txt b/README.txt new file mode 100644 --- /dev/null +++ b/README.txt @@ -0,0 +1,58 @@ +perceptualdiff - a program that compares two images using +a perceptually based image metric. +Copyright (C) 2006 Yangli Hector Yee + yeehector@users.sourceforge.net + http://pdiff.sourceforge.net/ +Go version Copyright (C) 2012 Sean Russell + +This program is free software; you can redistribute it and/or modify it +under the terms of version 2 of the GNU General Public License as published by +the Free Software Foundation. + +This program is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A +PARTICULAR PURPOSE. See the GNU General Public License for more details in the +file gpl.txt. + +Build Instructions +1. Download cross platform make from http://www.cmake.org +2. Download freeimage from https://sourceforge.net/projects/freeimage +3. Edit CMakeLists.txt to tell it where to find your free image build +4. Type cmake . +5. Type make . (or on Windows systems cmake makes a Visual Studio +Project file) +6. To specify the install directory, use make install DESTDIR="/home/me/mydist" + +Usage + +perceptualdiff image1.(tif | png) image2.(tif | png) [options] +-verbose : Turns on verbose mode +-fov deg: field of view, deg, in degrees. Usually between 10.0 to 85.0. +This controls how much of the screen the oberserver is seeing. Front row of +a theatre has a field of view of around 25 degrees. Back row has a field of + view of around 60 degrees. +-threshold p : Sets the number of pixels, p, to reject. For example if p is + 100, then the test fails if 100 or more pixels are perceptably different. +-gamma g : The gamma to use to convert to RGB linear space. Default is 2.2 +-luminance l: The luminance of the display the observer is seeing. Default + is 100 candela per meter squared +-colorfactor : How much of color to use, 0.0 to 1.0, 0.0 = ignore color. +-downsample : How many powers of two to down sample the image. +-output foo.ppm : Saves the difference image to foo.ppm + +Credits + +Hector Yee, project administrator and originator - hectorgon.blogspot.com +Scott Corley, for png file IO code +Tobias Sauerwein, for make install, package_source Cmake configuration +Cairo Team for bugfixes +Jim Tilander, Rewrote the IO to use FreeImage. + +Version History + +1.0 - Initial distribution +1.0.1 - Fixed off by one convolution error and libpng interface to 1.2.8 +1.0.2 - [jt] Converted the loading and saving routines to use FreeImage +1.1 - Added colorfactor and downsample options. Also always output +difference file if requested. Always print out differing pixels even if the test passes. +1.1.1 - Turn off color test in low lighting conditions. diff --git a/compareargs.go b/compareargs.go new file mode 100644 --- /dev/null +++ b/compareargs.go @@ -0,0 +1,74 @@ +package perceptualdiff + +import ( + "flag" + "fmt" +) + +/* +Comapre Args +Copyright (C) 2012 Sean Russell +Based entirely off the C++ code by Yangli Hector Yee + +This program is free softwareyou can redistribute it and/or modify it under +the terms of version 2 of the GNU General Public License as published by the +Free Software Foundation. + +This program is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTYwithout even the implied warranty of MERCHANTABILITY or FITNESS FOR A +PARTICULAR PURPOSE. See the GNU General Public License for more details. + +You should have received a copy of the GNU General Public License along with +this programif not, write to the Free Software Foundation, Inc., 59 Temple +Place, Suite 330, Boston, MA 02111-1307 USA +*/ + +const copyright = `PerceptualDiff version 1.1.1, Copyright (C) 2006 Yangli Hector Yee +PerceptualDiff comes with ABSOLUTELY NO WARRANTY +This is free software, and you are welcome +to redistribute it under certain conditions +See the GPL page for details: http://www.gnu.org/copyleft/gpl.html + +` + +// Args to pass into the comparison function +type CompareArgs struct { + ImgA *RGBAImage // Image A + ImgB *RGBAImage // Image B + ImgDiff *RGBAImage // Diff image + Verbose bool // Print lots of text or not + LuminanceOnly bool // Only consider luminanceignore chroma channels in the comparison. + FieldOfView float64 // Field of view in degrees + Gamma float64 // The gamma to convert to linear color space + Luminance float64 // the display's luminance + ThresholdPixels uint // How many pixels different to ignore + // How much color to use in the metric. + // 0.0 is the same as LuminanceOnly = true, + // 1.0 means full strength. + ColorFactor float64 + // How much to down sample image before comparing, in powers of 2. + DownSample int +} + + +func NewCompareArgs() *CompareArgs { + c := new(CompareArgs) + + c.ImgA = nil + c.ImgB = nil + c.ImgDiff = nil + c.FieldOfView = 45.0 + c.ThresholdPixels = 100 + c.Gamma = 2.2 + c.Luminance = 100.0 + c.ColorFactor = 1.0 + + return c +} + +func (c *CompareArgs) Print_Args() { + fmt.Printf("Field of view is %f degrees\n", c.FieldOfView) + fmt.Printf("Threshold pixels is %d pixels\n", c.ThresholdPixels) + fmt.Printf("The Gamma is %f\n", c.Gamma) + fmt.Printf("The Display's luminance is %f candela per meter squared\n", c.Luminance) +} diff --git a/gpl.txt b/gpl.txt new file mode 100644 --- /dev/null +++ b/gpl.txt @@ -0,0 +1,340 @@ + GNU GENERAL PUBLIC LICENSE + Version 2, June 1991 + + Copyright (C) 1989, 1991 Free Software Foundation, Inc. + 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. 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It is safest +to attach them to the start of each source file to most effectively +convey the exclusion of warranty; and each file should have at least +the "copyright" line and a pointer to where the full notice is found. + + + Copyright (C) + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + + +Also add information on how to contact you by electronic and paper mail. + +If the program is interactive, make it output a short notice like this +when it starts in an interactive mode: + + Gnomovision version 69, Copyright (C) year name of author + Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, the commands you use may +be called something other than `show w' and `show c'; they could even be +mouse-clicks or menu items--whatever suits your program. + +You should also get your employer (if you work as a programmer) or your +school, if any, to sign a "copyright disclaimer" for the program, if +necessary. Here is a sample; alter the names: + + Yoyodyne, Inc., hereby disclaims all copyright interest in the program + `Gnomovision' (which makes passes at compilers) written by James Hacker. + + , 1 April 1989 + Ty Coon, President of Vice + +This General Public License does not permit incorporating your program into +proprietary programs. If your program is a subroutine library, you may +consider it more useful to permit linking proprietary applications with the +library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. diff --git a/lpyramid.go b/lpyramid.go new file mode 100644 --- /dev/null +++ b/lpyramid.go @@ -0,0 +1,86 @@ +package perceptualdiff + +/* +Laplacian Pyramid +Copyright (C) 2012 Sean Russell +Based heavily on C++ code by Yangli Hector Yee + +This program is free software; you can redistribute it and/or modify it under +the terms of version 2 of the GNU General Public License as published by the +Free Software Foundation. + +This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY +without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. +See the GNU General Public License for more details. + +You should have received a copy of the GNU General Public License along with +this program; if not, write to the Free Software Foundation, Inc., 59 Temple +Place, Suite 330, Boston, MA 02111-1307 USA +*/ + +const MAX_PYR_LEVELS = 8 + +////////////////////////////////////////////////////////////////////// +// Construction/Destruction +////////////////////////////////////////////////////////////////////// + +type LPyramid struct { + Levels [][]float64 + Width, Height int +} + +var Kernel []float64 + +func init() { + Kernel = []float64{0.05, 0.25, 0.4, 0.25, 0.05} +} + +func NewLPyramid(image []float64, width, height int) *LPyramid { + rv := new(LPyramid) + rv.Levels = make([][]float64, MAX_PYR_LEVELS) + rv.Width, rv.Height = width, height + // Make the Laplacian pyramid by successively + // copying the earlier levels and blurring them + for i:=0; i=l.Width { nx=2*l.Width-nx-1 } + if ny>=l.Height { ny=2*l.Height-ny-1 } + a[index] += Kernel[i+2] * Kernel[j+2] * b[ny * l.Width + nx] + } + } + } + } +} + +func (p *LPyramid) Get_Value(x, y int, level uint) float64 { + index := x + y * p.Width + l := level + if l > MAX_PYR_LEVELS { + l = MAX_PYR_LEVELS + } + return p.Levels[level][index] +} diff --git a/metric.go b/metric.go new file mode 100644 --- /dev/null +++ b/metric.go @@ -0,0 +1,325 @@ +package perceptualdiff + +/* +Metric +Copyright (C) 2012 Sean Russell +Based heavily on C++ code by Yangli Hector Yee + +This program is free software; you can redistribute it and/or modify it under +the terms of version 2 of the GNU General Public License as published by the +Free Software Foundation. + +This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY +without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. +See the GNU General Public License for more details. + +You should have received a copy of the GNU General Public License along with +this program; if not, write to the Free Software Foundation, Inc., 59 Temple +Place, Suite 330, Boston, MA 02111-1307 USA +*/ + +import ( + . "math" + "fmt" + "image/color" +) + +/* +* Given the adaptation luminance, this function returns the +* threshold of visibility in cd per m^2 +* TVI means Threshold vs Intensity function +* This version comes from Ward Larson Siggraph 1997 +*/ +func tvi(adaption_luminance float64) float64 { + // returns the threshold luminance given the adaptation luminance + // units are candelas per meter squared + + var r float64 + log_a := Log10(adaption_luminance) + + if log_a < -3.94 { + r = -2.86 + } else if log_a < -1.44 { + r = Pow(0.405 * log_a + 1.6 , 2.18) - 2.86 + } else if log_a < -0.0184 { + r = log_a - 0.395 + } else if log_a < 1.9 { + r = Pow(0.249 * log_a + 0.65, 2.7) - 0.72 + } else { + r = log_a - 1.255 + } + + return Pow(10.0 , r) +} + + +// computes the contrast sensitivity function (Barten SPIE 1989) +// given the cycles per degree (cpd) and luminance (lum) +func csf(cpd, lum float64) (result float64) { + a := 440.0 * Pow((1.0 + 0.7 / lum), -0.2) + b := 0.3 * Pow((1.0 + 100.0 / lum), 0.15) + + result = a * cpd * Exp(-b * cpd) * Sqrt(1.0 + 0.06 * Exp(b * cpd)) + + return result +} + +/* +* Visual Masking Function +* from Daly 1993 +*/ +func mask(contrast float64) (result float64) { + a := Pow(392.498 * contrast, 0.7) + b := Pow(0.0153 * a, 4.0) + result = Pow(1.0 + b, 0.25) + + return result +} + +// convert Adobe RGB (1998) with reference white D65 to XYZ +func AdobeRGBToXYZ(r, g, b float64) (x, y, z float64) { + // matrix is from http://www.brucelindbloom.com/ + x = r * 0.576700 + g * 0.185556 + b * 0.188212 + y = r * 0.297361 + g * 0.627355 + b * 0.0752847 + z = r * 0.0270328 + g * 0.0706879 + b * 0.991248 + return +} + +type XYZ struct { + x, y, z float64 +} +func NewXYZ() XYZ { + return XYZ{-1,0,0} +} +const epsilon = 216.0 / 24389.0 +const kappa = 24389.0 / 27.0 + +func (xyz *XYZ) XYZToLAB(x, y, z float64) (L, A, B float64) { + // reference white + if xyz.x < 0 { + xyz.x, xyz.y, xyz.z = AdobeRGBToXYZ(1, 1, 1) + } + f := make([]float64, 3) + r := make([]float64, 3) + r[0] = x / xyz.x + r[1] = y / xyz.y + r[2] = z / xyz.z + for i := 0; i < 3; i++ { + if r[i] > epsilon { + f[i] = Pow(r[i], 1.0 / 3.0) + } else { + f[i] = (kappa * r[i] + 16.0) / 116.0 + } + } + L = 116.0 * f[1] - 16.0 + A = 500.0 * (f[0] - f[1]) + B = 200.0 * (f[1] - f[2]) + return +} + +func Yee_Compare(args *CompareArgs) bool { + for i := 0; i < args.DownSample; i++ { + if args.Verbose { + fmt.Printf("Downsampling by %d\n", 1 << uint(i+1)) + } + tmp, err := args.ImgA.DownSample() + if err == nil { + args.ImgA = tmp + } + tmp, err = args.ImgB.DownSample() + if err == nil { + args.ImgB = tmp + } + } + + bounds := args.ImgA.Bounds() + w, h := bounds.Dx(), bounds.Dy() + if ((w != args.ImgB.Bounds().Dx()) || (h != args.ImgB.Bounds().Dy())) { + fmt.Printf("Image dimensions do not match\n") + return false + } + + dim := w * h + identical := true + for ix := 0; ix < w; ix++ { + for iy := 0; iy < h; iy++ { + ca := args.ImgA.At(ix, iy).(color.RGBA) + cb := args.ImgB.At(ix, iy).(color.RGBA) + if ca.R != cb.R && ca.G != cb.G && ca.B != cb.B && ca.A != cb.A { + identical = false + break + } + } + } + if identical { + fmt.Printf("Images are binary identical\n") + return true + } + + // assuming colorspaces are in Adobe RGB (1998) convert to XYZ + aX := make([]float64, dim) + aY := make([]float64, dim) + aZ := make([]float64, dim) + bX := make([]float64, dim) + bY := make([]float64, dim) + bZ := make([]float64, dim) + aLum := make([]float64, dim) + bLum := make([]float64, dim) + + aA := make([]float64, dim) + bA := make([]float64, dim) + aB := make([]float64, dim) + bB := make([]float64, dim) + + if args.Verbose { + fmt.Printf("Converting RGB to XYZ\n") + } + + var x, y int + xyz := NewXYZ() + for y = 0; y < h; y++ { + for x = 0; x < w; x++ { + ra, ga, ba, _ := args.ImgA.At(x, y).RGBA() + // l is never actually used, AFAICT. Bug in original algo? + var r, g, b float64 + i := x + y * w + r = Pow(float64(ra) / 255.0, args.Gamma) + g = Pow(float64(ga) / 255.0, args.Gamma) + b = Pow(float64(ba) / 255.0, args.Gamma) + aX[i], aY[i], aZ[i] = AdobeRGBToXYZ(r,g,b) + _, aA[i], aB[i] = xyz.XYZToLAB(aX[i], aY[i], aZ[i]) + rb, gb, bb, _ := args.ImgA.At(x, y).RGBA() + r = Pow(float64(rb) / 255.0, args.Gamma) + g = Pow(float64(gb) / 255.0, args.Gamma) + b = Pow(float64(bb) / 255.0, args.Gamma) + bX[i],bY[i],bZ[i] = AdobeRGBToXYZ(r,g,b) + _, bA[i], bB[i] = xyz.XYZToLAB(bX[i], bY[i], bZ[i]) + aLum[i] = aY[i] * args.Luminance + bLum[i] = bY[i] * args.Luminance + } + } + + if args.Verbose { + fmt.Printf("Constructing Laplacian Pyramids\n") + } + + la := LPyramid{[][]float64{aLum}, w, h} + lb := LPyramid{[][]float64{bLum}, w, h} + + num_one_degree_pixels := (2.0 * Tan(args.FieldOfView * 0.5 * Pi / 180.0) * 180.0 / Pi) + pixels_per_degree := float64(w) / num_one_degree_pixels + + if (args.Verbose) { + fmt.Printf("Performing test\n") + } + + num_pixels := 1.0 + var adaptation_level uint + for i := uint(0); i < MAX_PYR_LEVELS; i++ { + adaptation_level = i + if num_pixels > num_one_degree_pixels { + break + } + num_pixels *= 2 + } + + cpd := make([]float64, MAX_PYR_LEVELS) + cpd[0] = 0.5 * pixels_per_degree + for i := 1; i < MAX_PYR_LEVELS; i++ { + cpd[i] = 0.5 * cpd[i - 1] + } + csf_max := csf(3.248, 100.0) + + F_freq := make([]float64, MAX_PYR_LEVELS - 2) + for i := 0; i < MAX_PYR_LEVELS - 2; i++ { + F_freq[i] = csf_max / csf(cpd[i], 100.0) + } + + var pixels_failed uint + for y = 0; y < h; y++ { + for x = 0; x < w; x++ { + index := x + y * w + contrast := make([]float64, MAX_PYR_LEVELS - 2) + var sum_contrast float64 + for i := uint(0); i < MAX_PYR_LEVELS - 2; i++ { + n1 := Abs(la.Get_Value(x,y,i) - la.Get_Value(x,y,i + 1)) + n2 := Abs(lb.Get_Value(x,y,i) - lb.Get_Value(x,y,i + 1)) + var numerator float64 + if n1 > n2 { numerator = n1 } else { numerator = n2 } + d1 := Abs(la.Get_Value(x,y,i+2)) + d2 := Abs(lb.Get_Value(x,y,i+2)) + denominator := d2 + if d1 > d2 { denominator = d1 } + if denominator < 1e-5 { denominator = 1e-5 } + contrast[i] = numerator / denominator + sum_contrast += contrast[i] + } + if sum_contrast < 1e-5 { sum_contrast = 1e-5 } + F_mask := make([]float64, MAX_PYR_LEVELS - 2) + adapt := la.Get_Value(x,y,adaptation_level) + lb.Get_Value(x,y,adaptation_level) + adapt *= 0.5 + if adapt < 1e-5 { adapt = 1e-5 } + for i := 0; i < MAX_PYR_LEVELS - 2; i++ { + F_mask[i] = mask(contrast[i] * csf(cpd[i], adapt)) + } + var factor float64 + for i := 0; i < MAX_PYR_LEVELS - 2; i++ { + factor += contrast[i] * F_freq[i] * F_mask[i] / sum_contrast + } + if factor < 1 { factor = 1 } + if factor > 10 { factor = 10 } + delta := Abs(la.Get_Value(x,y,0) - lb.Get_Value(x,y,0)) + pass := true + // pure luminance test + if delta > factor * tvi(adapt) { + pass = false + } else if !args.LuminanceOnly { + // CIE delta E test with modifications + color_scale := args.ColorFactor + // ramp down the color test in scotopic regions + if adapt < 10.0 { + // Don't do color test at all. + color_scale = 0.0 + } + da := aA[index] - bA[index] + db := aB[index] - bB[index] + da = da * da + db = db * db + delta_e := (da + db) * color_scale + if delta_e > factor { + pass = false + } + } + if !pass { + pixels_failed++ + if args.ImgDiff != nil { + args.ImgDiff.Set(x, y, color.RGBA{255, 0, 0, 255}) + } + } else { + if args.ImgDiff != nil { + args.ImgDiff.Set(x, y, color.RGBA{0, 0, 0, 255}) + } + } + } + } + + different := fmt.Sprintf("%d pixels are different\n", pixels_failed) + + // Always output image difference if requested. + if args.ImgDiff != nil { + if args.ImgDiff.WriteToFile(args.ImgDiff.Name) { + fmt.Printf("Wrote difference image to %s\n", args.ImgDiff.Name) + } else { + fmt.Printf("Could not write difference image to %s\n", args.ImgDiff.Name) + } + } + + if pixels_failed < args.ThresholdPixels { + fmt.Printf("Images are perceptually indistinguishable\n%s\n", different) + return true + } + + fmt.Printf("Images are visibly different\n%s\n", different) + + return false +} diff --git a/perceptualdiff/main.go b/perceptualdiff/main.go new file mode 100644 --- /dev/null +++ b/perceptualdiff/main.go @@ -0,0 +1,88 @@ +package main + +/* +PerceptualDiff - a program that compares two images using a perceptual metric +based on the paper : + A perceptual metric for production testing. + Journal of graphics tools, 9(4):33-40, 2004, Hector Yee +Copyright (C) 2012 Sean Russell +Based heavily on C++ code by Yangli Hector Yee + +This program is free software; you can redistribute it and/or modify it under +the terms of version 2 of the GNU General Public License as published by the +Free Software Foundation. + +This program is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A +PARTICULAR PURPOSE. See the GNU General Public License for more details. + +You should have received a copy of the GNU General Public License along with +this program; if not, write to the Free Software Foundation, Inc., 59 Temple +Place, Suite 330, Boston, MA 02111-1307 USA +*/ + +import ( + "perceptualdiff" + "os" +) + +func main() { + args := perceptualdiff.NewCompareArgs() + + if !parse_Args(args) { + os.Exit(-1) + } + + passed := perceptualdiff.Yee_Compare(args) + + if passed { + os.Exit(0) + } else { + os.Exit(1) + } +} + + +func parse_Args(c *CompareArgs) bool { + flag.BoolVar(&c.Verbose, "verbose", false, "Turns on verbose mode") + flag.Float64Var(&c.FieldOfView, "fov", 45.0, "Field of view in degrees (0.1 to 89.9)") + flag.UintVar(&c.ThresholdPixels, "threshold", 100, "#pixels p below which differences are ignored") + flag.Float64Var(&c.Gamma, "gamma", 2.2, "Value to convert rgb into linear space") + flag.Float64Var(&c.Luminance, "luminance", 100.0, "White luminance") + flag.BoolVar(&c.LuminanceOnly, "luminanceonly", false, "Only consider luminanceignore chroma (color) in the comparison") + flag.Float64Var(&c.ColorFactor, "colorfactor", 1.0, "How much of color to use, 0.0 to 1.0, 0.0 = ignore color.") + flag.IntVar(&c.DownSample, "downsample", 0, "How many powers of two to down sample the image.") + output_file_name := flag.String("output", "", "Write difference to a file") + flag.Usage = func() { + fmt.Printf(copyright) + fmt.Printf("PeceptualDiff \n\n") + fmt.Printf("Compares image1 and image2 using a perceptually based image metric\n") + flag.PrintDefaults() + fmt.Printf("Note: Input or Output files can also be in the PNG or JPG format ") + fmt.Printf("or any format\n") + fmt.Printf("that FreeImage supports.\n") + } + flag.Parse() + + if flag.NArg() < 2 { + flag.Usage() + return false + } + + var err error + c.ImgA, err = perceptualdiff.ReadFromFile(flag.Arg(0)) + if err != nil { + fmt.Printf("FAIL: Cannot open %s\n", flag.Arg(0)) + return false + } + c.ImgB, err = perceptualdiff.ReadFromFile(flag.Arg(1)) + if err != nil { + fmt.Printf("FAIL: Cannot open %s\n", flag.Arg(1)) + return false + } + + if *output_file_name != "" { + c.ImgDiff = NewRGBAImage(c.ImgA.Bounds().Dx(), c.ImgA.Bounds().Dy(), *output_file_name) + } + return true +} diff --git a/rgbaimage.go b/rgbaimage.go new file mode 100644 --- /dev/null +++ b/rgbaimage.go @@ -0,0 +1,129 @@ +package perceptualdiff + +import ( + "fmt" + "image" + "image/color" + "image/draw" + "image/jpeg" + "image/png" + "os" + "path" + _ "image/gif" +) + +/* +rgbaimage.go +Copyright (C) 2012 Sean E. Russell +Based heavily on C++ code by Yangli Hector Yee, which was rewritten by Jim Tilander + +This program is free software; you can redistribute it and/or modify it under +the terms of version 2 of the GNU General Public License as published by the +Free Software Foundation. + +This program is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A +PARTICULAR PURPOSE. See the GNU General Public License for more details. + +You should have received a copy of the GNU General Public License along with +this program; if not, write to the Free Software Foundation, Inc., 59 Temple +Place, Suite 330, Boston, MA 02111-1307 USA +*/ + +/** Class encapsulating an image containing R,G,B,A channels. + * + * Internal representation assumes data is in the ABGR format, with the RGB + * color channels premultiplied by the alpha value. Premultiplied alpha is + * often also called "associated alpha" - see the tiff 6 specification for some + * discussion - http://partners.adobe.com/asn/developer/PDFS/TN/TIFF6.pdf + * + */ + +type RGBAImage struct { + *image.RGBA + Name string +} + +func NewRGBAImage(w, h int, name string) *RGBAImage { + rv := new(RGBAImage) + rv.RGBA = image.NewRGBA(image.Rect(0, 0, w, h)) + if name != "" { + rv.Name = name + } + return rv +} + +type ImgError struct { + mesg string +} +func (i ImgError) Error() string { + return i.mesg +} + + +func (r *RGBAImage) DownSample() (*RGBAImage, error) { + b := r.Bounds() + if b.Dx() <= 1 || b.Dy() <= 1 { + return nil, ImgError{"bad boundaries"} + } + nw := b.Dx() / 2 + nh := b.Dy() / 2 + img := NewRGBAImage(nw, nh, r.Name) + for y := 0; y < nh; y++ { + for x := 0; x < nw; x++ { + d := make([]color.RGBA, 4) + // Sample a 2x2 patch from the parent image. + d[0] = r.At(2*x+0, 2*y+0).(color.RGBA) + d[1] = r.At(2*x+1, 2*y+0).(color.RGBA) + d[2] = r.At(2*x+0, 2*y+1).(color.RGBA) + d[3] = r.At(2*x+1, 2*y+1).(color.RGBA) + // Find the average color. + ra := (d[0].R + d[1].R + d[2].R + d[3].R) / 4 + rg := (d[0].G + d[1].G + d[2].G + d[3].G) / 4 + rb := (d[0].B + d[1].B + d[2].B + d[3].B) / 4 + img.Set(x, y, color.RGBA{ra, rg, rb, 255}) + } + } + return img, nil +} + +func (r *RGBAImage) WriteToFile(filename string) bool { + fout, err := os.Create(filename) + if err != nil { + fmt.Print(err) + return false + } + defer fout.Close() + switch path.Ext(filename) { + default: + fmt.Printf("Can't save to unknown filetype %s\n", filename) + fmt.Printf("Supported extensions are png, jpg, and jpeg\n") + return false + case "png", "PNG": + err = png.Encode(fout, r) + case "jpg", "jpeg", "JPG", "JPEG": + err = jpeg.Encode(fout, r, &jpeg.Options{100}) + } + if err != nil { + fmt.Print(err) + return false + } + return true +} + +func ReadFromFile(filename string) (*RGBAImage, error) { + fin, err := os.Open(filename) + if err != nil { + return nil, err + } + defer fin.Close() + + fimg, _, err := image.Decode(fin) + if err != nil { + return nil, err + } + b := fimg.Bounds() + rgba := image.NewRGBA(image.Rect(0, 0, b.Dx(), b.Dy())) + draw.Draw(rgba, rgba.Bounds(), fimg, b.Min, draw.Src) + return &RGBAImage{rgba, filename}, nil +}