OPGLES加載PNG圖片為紋理

【原創(chuàng)】OPGLES加載PNG圖片為紋理 因為BMP圖片在顯示的時候周邊有比較難看的鋸齒圖，OPGLES基本上都是使用對BMP加載紋理圖的做法，很少加載PNG紋理圖，今天在某國外網(wǎng)站看到這么一段使用OPGL加載PNG紋理圖代碼，摘錄下來。 論壇上有人試驗成功，但是我使用libpng庫的時候，用png_read_info讀取png圖片信息時出錯，正在調(diào)試中。大家討論討論。 通過該鏈接可以下載庫和源碼http://www.tenik.co.jp/~adachi/wince/zlibce/index.html

源碼如下：

1

/*

2

*

png.c

--

png

texture

loader

3

*

last

modification:

aug.

14,

2007

4

*

5

*

Copyright

(c)

2005-2007

David

HENRY

6

*

7

*

Permission

is

hereby

granted,

free

of

charge,

to

any

person

8

*

obtaining

a

copy

of

this

software

and

associated

documentation

9

*

files

(the

"Software"),

to

deal

in

the

Software

without

10

*

restriction,

including

without

limitation

the

rights

to

use,

11

*

copy,

modify,

merge,

publish,

distribute,

sublicense,

and/or

12

*

sell

copies

of

the

Software,

and

to

permit

persons

to

whom

the

13

*

Software

is

furnished

to

do

so,

subject

to

the

following

conditions:

14

*

15

*

The

above

copyright

notice

and

this

permission

notice

shall

be

16

*

included

in

all

copies

or

substantial

portions

of

the

Software.

17

*

18

*

THE

SOFTWARE

IS

PROVIDED

"AS

IS",

WITHOUT

WARRANTY

OF

ANY

KIND,

19

*

EXPRESS

OR

IMPLIED,

INCLUDING

BUT

NOT

LIMITED

TO

THE

WARRANTIES

OF

20

*

MERCHANTABILITY,

FITNESS

FOR

A

PARTICULAR

PURPOSE

AND

21

*

NONINFRINGEMENT.

22

*

IN

NO

EVENT

SHALL

THE

AUTHORS

OR

COPYRIGHT

HOLDERS

BE

LIABLE

FOR

23

*

ANY

CLAIM,

DAMAGES

OR

OTHER

LIABILITY,

WHETHER

IN

AN

ACTION

OF

24

*

CONTRACT,

TORT

OR

OTHERWISE,

ARISING

FROM,

OUT

OF

OR

IN

CONNECTION

25

*

WITH

THE

SOFTWARE

OR

THE

USE

OR

OTHER

DEALINGS

IN

THE

SOFTWARE.

26

*

27

*

gcc

-Wall

-ansi

-lGL

-lGLU

-lglut

28

*

`libpng12-config

--cflags

--libs`

png.c

-o

png

29

*/

30

31

#include

<GL/glut.h>

32

#include

<stdio.h>

33

#include

<stdlib.h>

34

#include

<string.h>

35

36

#include

<png.h>

37

38

/*

Microsoft

Visual

C++

*/

39

#ifdef

_MSC_VER

40

#pragma

comment

(lib,

"libpng.lib")

41

#pragma

comment

(lib,

"zlib.lib")

42

#pragma

comment

(linker,

"/nodefaultlib:libc")

43

#endif

/*

_MSC_VER

*/

44

45

/*

OpenGL

texture

info

*/

46

struct

gl_texture_t

47

{

48

GLsizei

width;

49

GLsizei

height;

50

51

GLenum

format;

52

GLint

internalFormat;

53

GLuint

id;

54

55

GLubyte

*texels;

56

};

57

58

/*

Texture

id

for

the

demo

*/

59

GLuint

texId;

60

61

62

static

void

63

GetPNGtextureInfo

(int

color_type,

struct

gl_texture_t

*texinfo)

64

{

65

switch

(color_type)

66

{

67

case

PNG_COLOR_TYPE_GRAY:

68

texinfo->format

=

GL_LUMINANCE;

69

texinfo->internalFormat

=

1;

70

break;

71

72

case

PNG_COLOR_TYPE_GRAY_ALPHA:

73

texinfo->format

=

GL_LUMINANCE_ALPHA;

74

texinfo->internalFormat

=

2;

75

break;

76

77

case

PNG_COLOR_TYPE_RGB:

78

texinfo->format

=

GL_RGB;

79

texinfo->internalFormat

=

3;

80

break;

81

82

case

PNG_COLOR_TYPE_RGB_ALPHA:

83

texinfo->format

=

GL_RGBA;

84

texinfo->internalFormat

=

4;

85

break;

86

87

default:

88

/*

Badness

*/

89

break;

90

}

91

}

92

93

static

struct

gl_texture_t

*

94

ReadPNGFromFile

(const

char

*filename)

95

{

96

struct

gl_texture_t

*texinfo;

97

png_byte

magic[8];

98

png_structp

png_ptr;

99

png_infop

info_ptr;

100

int

bit_depth,

color_type;

101

FILE

*fp

=

NULL;

102

png_bytep

*row_pointers

=

NULL;

103

png_uint_32

w,

h;

104

int

i;

105

106

/*

Open

image

file

*/

107

fp

=

fopen

(filename,

"rb");

108

if

(!fp)

109

{

110

fprintf

(stderr,

"error:

couldn't

open

\"%s\"!\n",

filename);

111

return

NULL;

112

}

113

114

/*

Read

magic

number

*/

115

fread

(magic,

1,

sizeof

(magic),

fp);

116

117

/*

Check

for

valid

magic

number

*/

118

if

(!png_check_sig

(magic,

sizeof

(magic)))

119

{

120

fprintf

(stderr,

"error:

\"%s\"

is

not

a

valid

PNG

image!\n",

121

filename);

122

fclose

(fp);

123

return

NULL;

124

}

125

126

/*

Create

a

png

read

struct

*/

127

png_ptr

=

png_create_read_struct

128

(PNG_LIBPNG_VER_STRING,

NULL,

NULL,

NULL);

129

if

(!png_ptr)

130

{

131

fclose

(fp);

132

return

NULL;

133

}

134

135

/*

Create

a

png

info

struct

*/

136

info_ptr

=

png_create_info_struct

(png_ptr);

137

if

(!info_ptr)

138

{

139

fclose

(fp);

140

png_destroy_read_struct

(&png_ptr,

NULL,

NULL);

141

return

NULL;

142

}

143

144

/*

Create

our

OpenGL

texture

object

*/

145

texinfo

=

(struct

gl_texture_t

*)

146

malloc

(sizeof

(struct

gl_texture_t));

147

148

/*

Initialize

the

setjmp

for

returning

properly

after

a

libpng

149

error

occured

*/

150

if

(setjmp

(png_jmpbuf

(png_ptr)))

151

{

152

fclose

(fp);

153

png_destroy_read_struct

(&png_ptr,

&info_ptr,

NULL);

154

155

if

(row_pointers)

156

free

(row_pointers);

157

158

if

(texinfo)

159

{

160

if

(texinfo->texels)

161

free

(texinfo->texels);

162

163

free

(texinfo);

164

}

165

166

return

NULL;

167

}

168

169

/*

Setup

libpng

for

using

standard

C

fread()

function

170

with

our

FILE

pointer

*/

171

png_init_io

(png_ptr,

fp);

172

173

/*

Tell

libpng

that

we

have

already

read

the

magic

number

*/

174

png_set_sig_bytes

(png_ptr,

sizeof

(magic));

175

176

/*

Read

png

info

*/

177

png_read_info

(png_ptr,

info_ptr);

178

179

/*

Get

some

usefull

information

from

header

*/

180

bit_depth

=

png_get_bit_depth

(png_ptr,

info_ptr);

181

color_type

=

png_get_color_type

(png_ptr,

info_ptr);

182

183

/*

Convert

index

color

images

to

RGB

images

*/

184

if

(color_type

==

PNG_COLOR_TYPE_PALETTE)

185

png_set_palette_to_rgb

(png_ptr);

186

187

/*

Convert

1-2-4

bits

grayscale

images

to

8

bits

188

grayscale.

*/

189

if

(color_type

==

PNG_COLOR_TYPE_GRAY

&&

bit_depth

<

8)

190

png_set_gray_1_2_4_to_8

(png_ptr);

191

192

if

(png_get_valid

(png_ptr,

info_ptr,

PNG_INFO_tRNS))

193

png_set_tRNS_to_alpha

(png_ptr);

194

195

if

(bit_depth

==

16)

196

png_set_strip_16

(png_ptr);

197

else

if

(bit_depth

<

8)

198

png_set_packing

(png_ptr);

199

200

/*

Update

info

structure

to

apply

transformations

*/

201

png_read_update_info

(png_ptr,

info_ptr);

202

203

/*

Retrieve

updated

information

*/

204

png_get_IHDR

(png_ptr,

info_ptr,

&w,

&h,

&bit_depth,

205

&color_type,

NULL,

NULL,

NULL);

206

texinfo->width

=

w;

207

texinfo->height

=

h;

208

209

/*

Get

image

format

and

components

per

pixel

*/

210

GetPNGtextureInfo

(color_type,

texinfo);

211

212

/*

We

can

now

allocate

memory

for

storing

pixel

data

*/

213

texinfo->texels

=

(GLubyte

*)malloc

(sizeof

(GLubyte)

*

texinfo->width

214

*

texinfo->height

*

texinfo->internalFormat);

215

216

/*

Setup

a

pointer

array.

Each

one

points

at

the

begening

of

a

row.

*/

217

row_pointers

=

(png_bytep

*)malloc

(sizeof

(png_bytep)

*

texinfo->height);

218

219

for

(i

=

0;

i

<

texinfo->height;

++i)

220

{

221

row_pointers[i]

=

(png_bytep)(texinfo->texels

+

222

((texinfo->height

-

(i

+

1))

*

texinfo->width

*

texinfo->internalFormat));

223

}

224

225

/*

Read

pixel

data

using

row

pointers

*/

226

png_read_image

(png_ptr,

row_pointers);

227

228

/*

Finish

decompression

and

release

memory

*/

229

png_read_end

(png_ptr,

NULL);

230

png_destroy_read_struct

(&png_ptr,

&info_ptr,

NULL);

231

232

/*

We

don't

need

row

pointers

anymore

*/

233

free

(row_pointers);

234

235

fclose

(fp);

236

return

texinfo;

237

}

238

239

GLuint

240

loadPNGTexture

(const

char

*filename)

241

{

242

struct

gl_texture_t

*png_tex

=

NULL;

243

GLuint

tex_id

=

0;

244

245

png_tex

=

ReadPNGFromFile

(filename);

246

247

if

(png_tex

&&

png_tex->texels)

248

{

249

/*

Generate

texture

*/

250

glGenTextures

(1,

&png_tex->id);

251

glBindTexture

(GL_TEXTURE_2D,

png_tex->id);

252

253

/*

Setup

some

parameters

for

texture

filters

and

mipmapping

*/

254

glTexParameteri

(GL_TEXTURE_2D,

GL_TEXTURE_MIN_FILTER,

GL_LINEAR_MIPMAP_LINEAR);

255

glTexParameteri

(GL_TEXTURE_2D,

GL_TEXTURE_MAG_FILTER,

GL_LINEAR);

256

257

#if

0

258

glTexImage2D

(GL_TEXTURE_2D,

0,

png_tex->internalFormat,

259

png_tex->width,

png_tex->height,

0,

png_tex->format,

260

GL_UNSIGNED_BYTE,

png_tex->texels);

261

#else

262

gluBuild2DMipmaps

(GL_TEXTURE_2D,

png_tex->internalFormat,

263

png_tex->width,

png_tex->height,

264

png_tex->format,

GL_UNSIGNED_BYTE,

png_tex->texels);

265

#endif

266

267

tex_id

=

png_tex->id;

268

269

/*

OpenGL

has

its

own

copy

of

texture

data

*/

270

free

(png_tex->texels);

271

free

(png_tex);

272

}

273

274

return

tex_id;

275

}

276

277

static

void

278

cleanup

()

279

{

280

glDeleteTextures

(1,

&texId);

281

}

282

283

static

void

284

init

(const

char

*filename)

285

{

286

/*

Initialize

OpenGL

*/

287

glClearColor

(1,

0.8f,

0.8f,0.0f);

288

glShadeModel

(GL_SMOOTH);

289

290

glEnable

(GL_DEPTH_TEST);

291

292

glEnable

(GL_BLEND);

293

glBlendFunc

(GL_SRC_ALPHA,

GL_ONE_MINUS_SRC_ALPHA);

294

295

/*

Load

PNG

texture

from

file

*/

296

texId

=

loadPNGTexture

(filename);

297

if

(!texId)

298

exit

(EXIT_FAILURE);

299

}

300

301

static

void

302

reshape

(int

w,

int

h)

303

{

304

if

(h

==

0)

305

h

=

1;

306

glViewport

(0,

0,

(GLsizei)w,

(GLsizei)h);

307

308

glMatrixMode

(GL_PROJECTION);

309

glLoadIdentity

();

310

gluPerspective

(45.0,

w/(GLdouble)h,

0.1,

1000.0);

311

312

glMatrixMode

(GL_MODELVIEW);

313

glLoadIdentity

();

314

315

glutPostRedisplay

();

316

}

317

318

static

void

319

display

()

320

{

321

glClear

(GL_COLOR_BUFFER_BIT

|

GL_DEPTH_BUFFER_BIT);

322

glLoadIdentity

();

323

324

glEnable

(GL_TEXTURE_2D);

325

glBindTexture

(GL_TEXTURE_2D,

texId);

326

327

/*

Draw

textured

quad

*/

328

glTranslatef

(0.0,

0.0,

-5.0);

329

glBegin

(GL_QUADS);

330

glTexCoord2f

(0.0f,

0.0f);

331

glVertex3f

(-1.0f,

-1.0f,

0.0f);

332

333

glTexCoord2f

(1.0f,

0.0f);

334

glVertex3f

(1.0f,

-1.0f,

0.0f);

335

336

glTexCoord2f

(1.0f,

1.0f);

337

glVertex3f

(1.0f,

1.0f