github.com/cellofellow/gopkg@v0.0.0-20140722061823-eec0544a62ad/image/webp/reader_test.go (about)

     1  // Copyright 2014 <chaishushan{AT}gmail.com>. 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 webp
     6  
     7  import (
     8  	"image"
     9  	"testing"
    10  
    11  	image_ext "github.com/chai2010/gopkg/image"
    12  	_ "github.com/chai2010/gopkg/image/png"
    13  )
    14  
    15  const testdataDir = "../testdata/"
    16  
    17  // TestDecode tests that decoding a PNG image and a BMP image result in the
    18  // same pixel data.
    19  func TestDecode(t *testing.T) {
    20  	img0, _, err := image_ext.Load(testdataDir+"video-001.png", nil)
    21  	if err != nil {
    22  		t.Fatal(err)
    23  	}
    24  
    25  	img1, _, err := image_ext.Load(testdataDir+"video-001.webp", nil)
    26  	if err != nil {
    27  		t.Fatal(err)
    28  	}
    29  
    30  	// Compare the average delta to the tolerance level.
    31  	want := int64(12 << 8)
    32  	if got := averageDelta(img0, img1); got > want {
    33  		t.Fatalf("average delta too high; got %d, want <= %d", got, want)
    34  	}
    35  }
    36  
    37  // averageDelta returns the average delta in RGB space. The two images must
    38  // have the same bounds.
    39  func averageDelta(m0, m1 image.Image) int64 {
    40  	b := m0.Bounds()
    41  	var sum, n int64
    42  	for y := b.Min.Y; y < b.Max.Y; y++ {
    43  		for x := b.Min.X; x < b.Max.X; x++ {
    44  			c0 := m0.At(x, y)
    45  			c1 := m1.At(x, y)
    46  			r0, g0, b0, _ := c0.RGBA()
    47  			r1, g1, b1, _ := c1.RGBA()
    48  			sum += delta(r0, r1)
    49  			sum += delta(g0, g1)
    50  			sum += delta(b0, b1)
    51  			n += 3
    52  		}
    53  	}
    54  	return sum / n
    55  }
    56  
    57  func delta(u0, u1 uint32) int64 {
    58  	d := int64(u0) - int64(u1)
    59  	if d < 0 {
    60  		return -d
    61  	}
    62  	return d
    63  }