Remove implicit bitmap to png conversions

The bitmap library used for this does not support the various bitmap
formats in the wild. This is also very confusing behaviour for a user of
the pre-v2 version of govips, which was able to handle all the various
bmp files

Closes davidbyttow#300

vips/foreign.go

@@ -6,12 +6,10 @@ import (
 	"bytes"
 	"encoding/xml"
 	"fmt"
-	"image/png"
 	"math"
 	"runtime"
 	"unsafe"
 
-	"golang.org/x/image/bmp"
 	"golang.org/x/net/html/charset"
 )
 
@@ -257,19 +255,8 @@ func vipsLoadFromBuffer(buf []byte, params *ImportParams) (*C.VipsImage, ImageTy
 	// Reference src here so it's not garbage collected during image initialization.
 	defer runtime.KeepAlive(src)
 
-	var err error
-
 	imageType := DetermineImageType(src)
 
-	if imageType == ImageTypeBMP {
-		src, err = bmpToPNG(src)
-		if err != nil {
-			return nil, ImageTypeUnknown, err
-		}
-
-		imageType = ImageTypePNG
-	}
-
 	if !IsTypeSupported(imageType) {
 		govipsLog("govips", LogLevelInfo, fmt.Sprintf("failed to understand image format size=%d", len(src)))
 		return nil, ImageTypeUnknown, ErrUnsupportedImageFormat
@@ -284,24 +271,6 @@ func vipsLoadFromBuffer(buf []byte, params *ImportParams) (*C.VipsImage, ImageTy
 	return importParams.outputImage, imageType, nil
 }
 
-func bmpToPNG(src []byte) ([]byte, error) {
-	i, err := bmp.Decode(bytes.NewReader(src))
-	if err != nil {
-		return nil, err
-	}
-
-	var w bytes.Buffer
-	pngEnc := png.Encoder{
-		CompressionLevel: png.NoCompression,
-	}
-	err = pngEnc.Encode(&w, i)
-	if err != nil {
-		return nil, err
-	}
-
-	return w.Bytes(), nil
-}
-
 func maybeSetBoolParam(p BoolParameter, cp *C.Param) {
 	if p.IsSet() {
 		C.set_bool_param(cp, toGboolean(p.Get()))

vips/image_test.go

@@ -132,22 +132,6 @@ func TestImageRef_HEIF_ftypmsf1(t *testing.T) {
 	assert.Equal(t, ImageTypeHEIF, metadata.Format)
 }
 
-func TestImageRef_BMP__ImplicitConversionToPNG(t *testing.T) {
-	Startup(nil)
-
-	raw, err := ioutil.ReadFile(resources + "bmp.bmp")
-	require.NoError(t, err)
-
-	img, err := NewImageFromBuffer(raw)
-	require.NoError(t, err)
-	require.NotNil(t, img)
-
-	exported, metadata, err := img.ExportNative()
-	assert.NoError(t, err)
-	assert.Equal(t, ImageTypePNG, metadata.Format)
-	assert.NotNil(t, exported)
-}
-
 func TestImageRef_SVG(t *testing.T) {
 	Startup(nil)
 

vips/resample.go

@@ -3,7 +3,6 @@ package vips
 // #include "resample.h"
 import "C"
 import (
-	"io/ioutil"
 	"runtime"
 	"unsafe"
 )
@@ -75,13 +74,7 @@ func vipsThumbnailFromFile(filename string, width, height int, crop Interesting,
 
 	if err := C.thumbnail(cFileName, &out, C.int(width), C.int(height), C.int(crop), C.int(size)); err != 0 {
 		err := handleImageError(out)
-		if src, err2 := ioutil.ReadFile(filename); err2 == nil {
-			if isBMP(src) {
-				if src2, err3 := bmpToPNG(src); err3 == nil {
-					return vipsThumbnailFromBuffer(src2, width, height, crop, size, params)
-				}
-			}
-		}
+
 		return nil, ImageTypeUnknown, err
 	}
 
@@ -109,11 +102,6 @@ func vipsThumbnailFromBuffer(buf []byte, width, height int, crop Interesting, si
 	}
 	if err != 0 {
 		err := handleImageError(out)
-		if isBMP(src) {
-			if src2, err2 := bmpToPNG(src); err2 == nil {
-				return vipsThumbnailFromBuffer(src2, width, height, crop, size, params)
-			}
-		}
 		return nil, ImageTypeUnknown, err
 	}