ebiten/graphics/opengl/texture.go

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package opengl
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// #cgo LDFLAGS: -framework OpenGL
//
// #include <OpenGL/gl.h>
import "C"
import (
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"image"
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"unsafe"
)
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func clp2(x uint64) uint64 {
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x -= 1
x |= (x >> 1)
x |= (x >> 2)
x |= (x >> 4)
x |= (x >> 8)
x |= (x >> 16)
x |= (x >> 32)
return x + 1
}
type Texture struct {
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id C.GLuint
width int
height int
textureWidth int
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textureHeight int
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}
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func createTexture(width, height int, pixels []uint8) *Texture {
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textureWidth := int(clp2(uint64(width)))
textureHeight := int(clp2(uint64(height)))
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if pixels != nil {
if width != textureWidth {
panic("sorry, but width should be power of 2")
}
if height != textureHeight {
panic("sorry, but height should be power of 2")
}
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}
texture := &Texture{
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id: 0,
width: width,
height: height,
textureWidth: textureWidth,
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textureHeight: textureHeight,
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}
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textureID := C.GLuint(0)
C.glGenTextures(1, (*C.GLuint)(&textureID))
if textureID == 0 {
panic("glGenTexture failed")
}
C.glPixelStorei(C.GL_UNPACK_ALIGNMENT, 4)
C.glBindTexture(C.GL_TEXTURE_2D, C.GLuint(textureID))
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ptr := unsafe.Pointer(nil)
if pixels != nil {
ptr = unsafe.Pointer(&pixels[0])
}
C.glTexImage2D(C.GL_TEXTURE_2D, 0, C.GL_RGBA,
C.GLsizei(textureWidth), C.GLsizei(textureHeight),
0, C.GL_RGBA, C.GL_UNSIGNED_BYTE, ptr)
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C.glTexParameteri(C.GL_TEXTURE_2D, C.GL_TEXTURE_MAG_FILTER, C.GL_LINEAR)
C.glTexParameteri(C.GL_TEXTURE_2D, C.GL_TEXTURE_MIN_FILTER, C.GL_LINEAR)
C.glBindTexture(C.GL_TEXTURE_2D, 0)
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texture.id = textureID
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return texture
}
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type textureError string
func (err textureError) Error() string {
return "Texture Error: " + string(err)
}
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func newTexture(width, height int) *Texture {
return createTexture(width, height, nil)
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}
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func newTextureFromImage(img image.Image) (*Texture, error) {
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var pix []uint8
switch img.(type) {
case *image.RGBA:
pix = img.(*image.RGBA).Pix
case *image.NRGBA:
pix = img.(*image.NRGBA).Pix
default:
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return nil, textureError("image format must be RGBA or NRGBA")
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}
size := img.Bounds().Size()
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return createTexture(size.X, size.Y, pix), nil
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}