github.com/tcnksm/go@v0.0.0-20141208075154-439b32936367/src/image/decode_test.go (about)

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package image_test
     6  
     7  import (
     8  	"bufio"
     9  	"image"
    10  	"image/color"
    11  	"os"
    12  	"testing"
    13  
    14  	_ "image/gif"
    15  	_ "image/jpeg"
    16  	_ "image/png"
    17  )
    18  
    19  type imageTest struct {
    20  	goldenFilename string
    21  	filename       string
    22  	tolerance      int
    23  }
    24  
    25  var imageTests = []imageTest{
    26  	{"testdata/video-001.png", "testdata/video-001.png", 0},
    27  	// GIF images are restricted to a 256-color palette and the conversion
    28  	// to GIF loses significant image quality.
    29  	{"testdata/video-001.png", "testdata/video-001.gif", 64 << 8},
    30  	{"testdata/video-001.png", "testdata/video-001.interlaced.gif", 64 << 8},
    31  	{"testdata/video-001.png", "testdata/video-001.5bpp.gif", 128 << 8},
    32  	// JPEG is a lossy format and hence needs a non-zero tolerance.
    33  	{"testdata/video-001.png", "testdata/video-001.jpeg", 8 << 8},
    34  	{"testdata/video-001.png", "testdata/video-001.progressive.jpeg", 8 << 8},
    35  	// Grayscale images.
    36  	{"testdata/video-005.gray.png", "testdata/video-005.gray.jpeg", 8 << 8},
    37  	{"testdata/video-005.gray.png", "testdata/video-005.gray.png", 0},
    38  }
    39  
    40  func decode(filename string) (image.Image, string, error) {
    41  	f, err := os.Open(filename)
    42  	if err != nil {
    43  		return nil, "", err
    44  	}
    45  	defer f.Close()
    46  	return image.Decode(bufio.NewReader(f))
    47  }
    48  
    49  func decodeConfig(filename string) (image.Config, string, error) {
    50  	f, err := os.Open(filename)
    51  	if err != nil {
    52  		return image.Config{}, "", err
    53  	}
    54  	defer f.Close()
    55  	return image.DecodeConfig(bufio.NewReader(f))
    56  }
    57  
    58  func delta(u0, u1 uint32) int {
    59  	d := int(u0) - int(u1)
    60  	if d < 0 {
    61  		return -d
    62  	}
    63  	return d
    64  }
    65  
    66  func withinTolerance(c0, c1 color.Color, tolerance int) bool {
    67  	r0, g0, b0, a0 := c0.RGBA()
    68  	r1, g1, b1, a1 := c1.RGBA()
    69  	r := delta(r0, r1)
    70  	g := delta(g0, g1)
    71  	b := delta(b0, b1)
    72  	a := delta(a0, a1)
    73  	return r <= tolerance && g <= tolerance && b <= tolerance && a <= tolerance
    74  }
    75  
    76  func TestDecode(t *testing.T) {
    77  	golden := make(map[string]image.Image)
    78  loop:
    79  	for _, it := range imageTests {
    80  		g := golden[it.goldenFilename]
    81  		if g == nil {
    82  			var err error
    83  			g, _, err = decode(it.goldenFilename)
    84  			if err != nil {
    85  				t.Errorf("%s: %v", it.goldenFilename, err)
    86  				continue loop
    87  			}
    88  			golden[it.goldenFilename] = g
    89  		}
    90  		m, imageFormat, err := decode(it.filename)
    91  		if err != nil {
    92  			t.Errorf("%s: %v", it.filename, err)
    93  			continue loop
    94  		}
    95  		b := g.Bounds()
    96  		if !b.Eq(m.Bounds()) {
    97  			t.Errorf("%s: want bounds %v got %v", it.filename, b, m.Bounds())
    98  			continue loop
    99  		}
   100  		for y := b.Min.Y; y < b.Max.Y; y++ {
   101  			for x := b.Min.X; x < b.Max.X; x++ {
   102  				if !withinTolerance(g.At(x, y), m.At(x, y), it.tolerance) {
   103  					t.Errorf("%s: at (%d, %d), want %v got %v", it.filename, x, y, g.At(x, y), m.At(x, y))
   104  					continue loop
   105  				}
   106  			}
   107  		}
   108  		if imageFormat == "gif" {
   109  			// Each frame of a GIF can have a frame-local palette override the
   110  			// GIF-global palette. Thus, image.Decode can yield a different ColorModel
   111  			// than image.DecodeConfig.
   112  			continue
   113  		}
   114  		c, _, err := decodeConfig(it.filename)
   115  		if m.ColorModel() != c.ColorModel {
   116  			t.Errorf("%s: color models differ", it.filename)
   117  			continue loop
   118  		}
   119  	}
   120  }